Evidence for a direct central anorectic effect of tumor-necrosis-factor-alpha in the rat

Anti-Inflammatory Effect of Ethanolic Extract from Tabebuia rosea (Bertol.) DC., Quercetin, and Anti-Obesity Drugs in Adipose Tissue in Wistar Rats with Diet-Induced Obesity

Obesity is characterized by the excessive accumulation of fat, which triggers a low-grade chronic inflammatory process. Currently, the search for compounds with anti-obesogenic effects that help reduce body weight, as well as associated comorbidities, continues. Among this group of compounds are plant extracts and flavonoids with a great diversity of action mechanisms associated with their beneficial effects, such as anti-inflammatory effects and/or as signaling molecules. In the bark of Tabebuia rosea tree, there are different classes of metabolites with anti-inflammatory properties, such as quercetin. Therefore, the present work studied the effect of the ethanolic extract of T. rosea and quercetin on the mRNA of inflammation markers in obesity compared to the drugs currently used. Total RNA was extracted from epididymal adipose tissue of high-fat diet-induced obese Wistar rats treated with orlistat, phentermine, T. rosea extract, and quercetin. The rats treated with T. rosea and quercetin showed 36 and 31% reductions in body weight compared to the obese control, and they likewise inhibited pro-inflammatory molecules: Il6, Il1b, Il18, Lep, Hif1a, and Nfkb1 without modifying the expression of Socs1 and Socs3. Additionally, only T. rosea overexpressed Lipe. Both T. rosea and quercetin led to a reduction in the expression of pro-inflammatory genes, modifying signaling pathways, which led to the regulation of the obesity-inflammation state.

Impacts of stress-induced inflammation on feed intake of beef cattle

Livestock animals are often exposed to unavoidable stressful situations during their productive life that triggers stress-induced inflammatory responses, which are known to influence their nutrient requirements and feed intake. Decreased growth performance and immunocompetence of stressed livestock are often the main consequence of reduced feed intake. Because feed intake is usually reduced in animals experiencing stress conditions, concentrations of certain nutrients in the diets typically need to be increased to meet the requirements of the animals. Therefore, understanding the mechanisms that control feed intake in animals experiencing stress-induced inflammation is essential for increasing intake, milk or meat production, feed efficiency, and animal health. This review highlights the hormones regulating feed intake in ruminants and how stress-induced inflammation affect these hormones at local and systemic levels. The mechanism of feed intake regulation in ruminants is extremely complex and involves multiple controls. The liver is an important sensor of energy status in animals under homeostatic conditions, which transmits signals to brain feeding centers that modulate appetite. However, the physiologic consequences associated with different stressors will rearrange the hierarchy of mechanisms controlling feed intake compared to animals under homeostatic conditions, and other tissues (e.g., intestines), systems (e.g., endocrine and lymphatic) hormones (e.g., leptin and ghrelin) will directly affect intake regulation during stress and inflammatory conditions. It is suggested that the immune system can interact with the central nervous system to modulate feed intake. As example, stress events elicit numerous stressors that increase circulating proinflammatory cytokines, including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), and IL-8, and acute-phase proteins (APP), and the magnitude of these responses are negatively correlated with feed intake. A direct effect of these cytokines on rumen microbial fermentation and intestinal barrier function was also reported and might indirectly affect intake regulation in ruminants. This review describes the main hormones and proinflammatory cytokines involved in stress-induced inflammation and how they can directly or indirectly affect intake regulation in ruminants. Understanding the mechanisms controlling feed intake in ruminants will help producers to implement management and feed strategies to optimize productivity and profitability in stressed livestock species.

Glial cells in anorexia

Anorexia is a loss of appetite or an inability to eat and is often associated with eating disorders. However, animal anorexia is physiologically regulated as a part of the life cycle; for instance, during hibernation, migration or incubation. Anorexia nervosa (AN), on the other hand, is a common eating disorder among adolescent females that experience an intense fear of gaining weight due to body image distortion that results in voluntary avoidance of food intake and, thus, severe weight loss. It has been shown that the neurobiology of feeding extends beyond the hypothalamus. The prefrontal cortex (PFC) is involved in food choice and body image perception, both relevant in AN. However, little is known about the neurobiology of AN, and the lack of effective treatments justifies the use of animal models. Glial cells, the dominant population of nerve cells in the central nervous system, are key in maintaining brain homeostasis. Accordingly, recent studies suggest that glial function may be compromised by anorexia. In this review, we summarize recent findings about anorexia and glial cells.

Invited review: Mechanisms of hypophagia during disease

Suppression of appetite, or hypophagia, is among the most recognizable effects of disease in livestock, with the potential to impair growth, reproduction, and lactation. The continued evolution of the field of immunology has led to a greater understanding of the immune and endocrine signaling networks underlying this conserved response to disease. Inflammatory mediators, especially including the cytokines tumor necrosis factor-α and interleukin-1β, are likely pivotal to disease-induced hypophagia, based on findings in both rodents and cattle. However, the specific mechanisms linking a cytokine surge to decreased feeding behavior are more difficult to pin down and likely include direct effects on appetite centers in the brain, alteration of gastric motility, and modulation of other endocrine factors that influence appetite and satiety. These insights into the mechanisms for disease-induced hypophagia have great relevance for management of neonatal calves, mature cows transitioning to lactation, and cows experiencing mastitis; however, it is not necessarily the case that increasing feed intake by any means possible will improve health outcomes for diseased cattle. We explore conflicting effects of hypophagia on immune responses, which may be impaired by the lack of specific substrates, versus apparent benefits for controlling the growth of some pathogens. Anti-inflammatory strategies have shown promise for promoting recovery of feed intake following some conditions but not others. Finally, we explore the potential for early disease detection through automated monitoring of feeding behavior and consider which strategies may be implemented to respond to early hypophagia.

Anorexia induces a microglial associated pro-inflammatory environment and correlates with neurodegeneration in the prefrontal cortex of young female rats

Dehydration-Induced Anorexia (DIA) is a murine model that reproduces weight loss and avoidance of food, despite its availability. The prefrontal cortex (PFC) integrates sensory inputs and updates associative learning to promote (hunger) or inhibit (satiety) food-seeking behavior. In this study we tested if anorexia induces a pro-inflammatory environment associated with microglia in the medial prefrontal cortex (mPFC) and orbitofrontal cortex (OFC), specific subregions of the PFC involved in appetite. Our results showed that anorexia increased microglial density, promoted a de-ramified morphology and augmented the de-ramified/ramified ratio in the mPFC and OFC but not in the motor cortex. Anorexia also increased the expression of the pro-inflammatory cytokines TNF-α, IL-6 and IL-1β. This pro-inflammatory environment associated with microglia activation correlates with neuronal damage as revealed by Fluoro Jade C (FJC) and NeuN immunolabeling. We conclude that anorexia triggers a pro-inflammatory environment associated with microglia that correlates with neurodegeneration in the mPFC and OFC.

Helicobacter Pylori Infection: A New Cause of Anorexia in Peritoneal Dialysis Patients

♦ Objective

Helicobacter pylori (HP) infection has frequently been found in dialysis patients. Chronic infections induce overproduction of pro-inflammatory substances. Inflammation has been associated with cachexia and anorexia. We explored the relationship between HP infection, anorexia, and malnutrition in peritoneal dialysis (PD) patients.

♦ Patients and Methods

The study included 48 clinically stable PD patients divided into four groups: HP+ with anorexia (group I, n = 12); HP+ without anorexia (group II, n = 4); HP- with anorexia (group III, n = 5); and HP- without anorexia (group IV, n = 27). Infection with HP was diagnosed by breath test. Anorexia was evaluated using a personal interview and an eating motivation scale (VAS). The VAS included five questions that are answered before and after eating. The questions concern desire to eat, hunger, feeling of fullness, prospective consumption, and palatability. Biochemical markers of nutrition and inflammation were also determined.

♦ Results

At baseline, group I showed lower scores for desire to eat, hunger sensation, prospective consumption, and palatability. They also showed lower lymphocyte counts, prealbumin, transferrin, serum albumin, normalized equivalent of protein–nitrogen appearance (nPNA), and residual renal function (RRF). In addition, the same group showed higher levels of C-reactive protein (CRP) and more sensation of fullness than the remaining groups. In the entire series, we found significant linear correlations between the following markers of nutrition and certain questions on the VAS: albumin with before-lunch desire to eat ( r = 0.38, p < 0.05), and prealbumin with before-lunch hunger ( r = 0.41, p < 0.05) and after-lunch hunger ( r = -0.35, p < 0.05). Negative linear correlations were found between albumin and fullness before lunch ( r = -0.45, p < 0.01), and between prealbumin and before-lunch desire to eat ( r = -0.39, p < 0.05). Negative linear correlations were also seen between CRP and albumin ( r = -0.35, p < 0.05) and between CRP and prealbumin ( r = -0.36, p < 0.05). Similarly, CRP showed a negative correlation with before-lunch desire to eat ( r = -0.38, p < 0.05) and after-lunch desire to eat ( r = -0.45, p < 0.01). After HP eradication, group I showed a significant increase in markers of nutrition and in VAS scores for almost all questions. Simultaneously, they showed a decrease in CRP level. Significant differences were also found in lymphocyte count (1105 ± 259.4 cells/mm3 vs 1330.8 ± 316 cells/mm3, p < 0.05), nPNA (0.9 ± 0.16 g/kg/day vs 1.07 ± 0.3 g/kg/day, p < 0.05), prealbumin (26.7 ± 6.5 mg/dL vs 33.9 ± 56.6 mg/dL, p < 0.01), albumin (3.48 ± 0.3 g/dL vs 3.67 ± 0.35 g/dL, p < 0.05), CRP (1.16 ± 1.14 mg/dL vs 0.88 ± 1.2 mg/dL, p < 0.054), before-lunch desire to eat (56.6 ± 6.8 vs 72.2 ± 4, p < 0.001), after-lunch desire to eat (5.4 ± 2.6 vs 12.3 ± 2, p < 0.01), hunger before lunch (55.4 ± 5.4 vs 73.1 ± 4.6, p < 0.001), hunger after lunch (5.8 ± 2.9 vs 11 ± 4, p < 0.01), fullness before lunch (36.6 ± 10.3 vs 18.7 ± 8.8, p < 0.001), consumption after lunch (5 ± 4.7 vs 17.5 ± 18, p < 0.05), and palatability (61 ± 5.3 vs 74.1 ± 4.1, p < 0.001).

♦ Conclusion

Infection with HP is associated with anorexia, inflammation, and malnutrition in PD patients. Eradication of HP significantly improves this syndrome. Residual renal function seem to have a protective effect on appetite preservation. The present study supports the hypothesis of the involvement of inflammation in the pathogenesis of malnutrition in PD patients.

Uremic Anorexia: A Consequence of Persistently High Brain Serotonin Levels? The Tryptophan/Serotonin Disorder Hypothesis

Anorexia is a frequent part of uremic syndrome, contributing to malnutrition in dialysis patients. Many factors have been suggested as responsible for uremic anorexia.

In this paper we formulate a new hypothesis to explain the appetite disorders in dialysis patients: “the tryptophan/serotonin disorder hypothesis.” We review current knowledge of normal hunger–satiety cycle control and the disorders described in uremic patients. There are four phases in food intake regulation: ( 1 ) the gastric phase, during which food induces satiety through gastric distention and satiety peptide release; ( 2 ) the post absorptive phase, during which circulating compounds, including glucose and amino acids, cause satiety by hepatic receptors via the vagus nerve; ( 3 ) the hepatic phase, during which adenosine triphosphate (ATP) concentration is the main stimulus inducing hunger or satiety, with cytokines inhibiting ATP production; and ( 4 ) the central phase, during which appetite is regulated through peripheral (circulating plasma substances and neurotransmitters) and brain stimuli. Brain serotonin is the final target for peripheral mechanisms controlling appetite. High brain serotonin levels and a lower serotonin/ dopamine ratio cause anorexia. Plasma and brain amino acid concentrations are recognized factors involved in neurotransmitter synthesis and appetite control. Tryptophan is the substrate of serotonin synthesis. High plasma levels of anorectics such as tryptophan (plasma and brain), cholecystokinin, tumor necrosis factor alpha, interleukin-1, and leptin, and deficiencies of nitric oxide and neuropeptide Y have been described in uremia; all increase intracerebral serotonin.

We suggest that brain serotonin hyperproduction due to a uremic-dependent excess of tryptophan may be the final common pathway involved in the genesis of uremic anorexia. Various methods of ameliorating anorexia by decreasing the central effects of serotonin are proposed.

Phospholipase C-related catalytically inactive protein regulates lipopolysaccharide-induced hypothalamic inflammation-mediated anorexia in mice

Peripheral lipopolysaccharide (LPS) injection induces systemic inflammation through the activation of the inhibitor of nuclear factor kappa B (NF-κB) kinase (IKK)/NF-κB signaling pathway, which promotes brain dysfunction resulting in conditions including anorexia. LPS-mediated reduction of food intake is associated with activation of NF-κB signaling and phosphorylation of the transcription factor signal transducer and activator of transcription 3 (STAT3) in the hypothalamus. We recently reported phospholipase C-related catalytically inactive protein (PRIP) as a new negative regulator of phosphatidylinositol 3-kinase/AKT signaling. AKT regulates the IKK/NF-κB signaling pathway; therefore, this study aimed to investigate the role of PRIP/AKT signaling in LPS-mediated neuroinflammation-induced anorexia. PRIP gene (Prip1 and Prip2) knockout (Prip-KO) mice intraperitoneally (ip) administered with LPS exhibited increased anorexia responses compared with wild-type (WT) controls. Although few differences were observed between WT and Prip-KO mice in LPS-elicited plasma pro-inflammatory cytokine elevation, hypothalamic pro-inflammatory cytokines were significantly upregulated in Prip-KO rather than WT mice. Hypothalamic AKT and IKK phosphorylation and IκB degradation were significantly increased in Prip-KO rather than WT mice, indicating further promotion of AKT-mediated NF-κB signaling. Consistently, hypothalamic STAT3 was further phosphorylated in Prip-KO rather than WT mice. Furthermore, suppressor of cytokine signaling 3 (Socs3), a negative feedback regulator for STAT3 signaling, and cyclooxogenase-2 (Cox2), a candidate molecule in LPS-induced anorexigenic responses, were upregulated in the hypothalamus in Prip-KO rather than WT mice. Pro-inflammatory cytokines were upregulated in hypothalamic microglia isolated from Prip-KO rather than WT mice. Together, these findings indicate that PRIP negatively regulates LPS-induced anorexia caused by pro-inflammatory cytokine expression in the hypothalamus, which is mediated by AKT-activated NF-κB signaling. Importantly, hypothalamic microglia participate in this PRIP-mediated process. Elucidation of PRIP-mediated neuroinflammatory responses may provide novel insights into the pathophysiology of many brain dysfunctions.

Anorexia increases microglial density and cytokine expression in the hippocampus of young female rats

Anorexia by osmotic dehydration is an adaptive response to hypernatremia and hyperosmolaemia induced by ingestion of a hypertonic solution. Dehydration-induced anorexia (DIA) reproduces weight loss and avoidance of food, despite its availability. By using this model, we previously showed increased reactive astrocyte density in the rat dorsal hippocampus, suggesting a pro-inflammatory environment where microglia may play an important role. However, whether such anorexic condition increases a pro-inflammatory response is unknown. The aim of this study was to test if DIA increases microglial density in the dorsal hippocampus, as well as the expression of pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6) and interleukin 1 beta (IL-1β) in the hippocampus of young female rats. Our results showed that DIA significantly increased microglial density in CA2-CA3 and dentate gyrus (DG) but not in CA1. However, forced food restriction (FFR) only increased microglial density in the DG. Accordingly, the activated/resting microglia ratio was significantly increased in CA2-CA3 and DG, in DIA and FFR groups. Finally, western blot analysis showed increased expression of IBA1, TNF-α, IL-6 and IL-1β in the hippocampus of both experimental groups. We conclude that anorexia triggers increased reactive microglial density and expression of TNF-α, IL-6 and IL-1β; this environment may result in hippocampal neuroinflammation.

Effect of central injection of tumor-necrosis factor-like cytokine 1A and interferons on food intake in chicks

In mammals, anorexia accompanying infection is thought to be mediated via cytokines including interleukins, interferons (IFNs), and tumor necrosis factor (TNF). However, there is a lack of related knowledge on birds. Therefore, the purpose of the present study was to determine if cytokines are associated with reduced food intake in chicks (Gallus gallus). Specifically, we evaluated the effects of TNF-like cytokine 1A (TL1A), a member of the TNF family, interferon-α (IFN-α), and interferon-γ (IFN-γ) on food intake. Additionally, the effect of lipopolysaccharide (LPS) and polyinosinic:polycytidylic acid (poly I:C) on cytokine mRNA expression in the diencephalon and spleen was also measured. Intracerebroventricular (ICV) injection of 0.05 or 0.5 μg TL1A, IFN-α, and IFN-γ had no effect on food intake. However, when 1.0 μg each of these factors was evaluated, TL1A significantly decreased food intake at 180 and 240 min after the injection, but IFN-α and IFN-γ had no effect. When chicks received intraperitoneal (IP) injections of 100 μg LPS or 400 μg poly I:C, their food intake was reduced. Diencephalic mRNA expression of TL1A was significantly decreased following IP injection of LPS or poly I:C. Additionally, diencephalic mRNA expression of IFN-γ mRNA was significantly increased by IP injection of LPS but decreased by IP injection of poly I:C. For the spleen, IP injection of LPS and poly I:C both significantly increased TL1A and IFN-γ mRNA expression. In sum, we have provided evidence that central TL1A but not IFN-α or IFN-γ are related to reduction of food intake in chicks, but the role of these cytokines for mediating anorexia associated with infections may differ from mammals.

AMP-activated protein kinase (AMPK) activator A-769662 increases intracellular calcium and ATP release from astrocytes in an AMPK-independent manner

AIM

To test the hypothesis that, given the role of AMP-activated protein kinase (AMPK) in regulating intracellular ATP levels, AMPK may alter ATP release from astrocytes, the main sources of extracellular ATP (eATP) within the brain.

MATERIALS AND METHODS

Measurements of ATP release were made from human U373 astrocytoma cells, primary mouse hypothalamic (HTAS) and cortical astrocytes (CRTAS) and wild-type and AMPK α1/α2 null mouse embryonic fibroblasts (MEFs). Cells were treated with drugs known to modulate AMPK activity: A-769662, AICAR and metformin, for up to 3 hours. Intracellular calcium was measured using Fluo4 and Fura-2 calcium-sensitive fluorescent dyes.

RESULTS

In U373 cells, A-769662 (100 μM) increased AMPK phosphorylation, whereas AICAR and metformin (1 mM) induced a modest increase or had no effect, respectively. Only A-769662 increased eATP levels, and this was partially blocked by AMPK inhibitor Compound C. A-769662-induced increases in eATP were preserved in AMPK α1/α2 null MEF cells. A-769662 increased intracellular calcium in U373, HTAS and CRTAS cells and chelation of intracellular calcium using BAPTA-AM reduced A-769662-induced eATP levels. A-769662 also increased ATP release from a number of other central and peripheral endocrine cell types.

CONCLUSIONS

AMPK is required to maintain basal eATP levels but is not required for A-769662-induced increases in eATP. A-769662 (>50 μM) enhanced intracellular calcium levels leading to ATP release in an AMPK and purinergic receptor independent pathway.

Hypothalamic Neuronal Histamine Modulates Febrile Response but Not Anorexia Induced by Lipopolysaccharide

This study examined the contribution of hypothalamic neuronal histamine (HA) to the anorectic and febrlle responses induced by lipopolysaccharide (LPS), an exogenous pyrogen, and the endogenous pyrogens interleukin-1β (IL-1β) and tumor necrosis factor-α (TNF-α). Intraperitoneal (ip) Injection of LPS, IL-1β, or TNF-α suppressed 24-hr cumulative food intake and increased rectal temperature in rats.

To analyze the histamlnergic contribution, rats were pre-treated with intracerebroventricular (icv) injection of 2.44 mmol/ kg or ip injection of 244 mmol/kg of α-fluoromethylhistidine (FMH), a suicide inhibitor of histidine decarboxylase (HDC), to deplete Neural HA. The depletion of neural HA augmented the febrile response to ip Injection of LPS and IL-1ß and alleviated the anorectic response to ip injection of IL-1ß. However, the depletion of neural HA did not modify the LPS-lnduced anorectic response or TNF-α-induced febrile and anorectic responses. Consistent with these results, the rate of hypothalamic HA turnover, assessed by the accumulation of tele-methylhistamine (t-MH), was elevated with ip injections of LPS and IL-1ß, but unaffected by TNF-α at equivalent doses. This suggests that (I) LPS and IL-1ß activate hypothalamic neural HA turnover; (II) hypothalamic neural HA suppresses the LPS- and IL-1β-induced febrile responses and accelerates the IL-1ß-induced anorectic response; and (iii) TNF-α modulates the febrile and anorectic responses via a neural HA-independent pathway. Therefore, hypothalamic neural HA is Involved in the IL-1ß-dominant pathway, rather than the TNF-α-dominant pathway, preceding the systemic Inflammatory response induced by exogenous pyrogens, such as LPS. Further research on this is needed.

Lipopolysacharide Rapidly and Completely Suppresses AgRP Neuron-Mediated Food Intake in Male Mice

Although Agouti-related peptide (AgRP) neurons play a key role in the regulation of food intake, their contribution to the anorexia caused by proinflammatory insults has yet to be identified. Using a combination of neuroanatomical and pharmacogenetics experiments, this study sought to investigate the importance of AgRP neurons and downstream targets in the anorexia caused by the peripheral administration of a moderate dose of lipopolysaccharide (LPS) (100 μg/kg, ip). First, in the C57/Bl6 mouse, we demonstrated that LPS induced c-fos in select AgRP-innervated brain sites involved in feeding but not in any arcuate proopiomelanocortin neurons. Double immunohistochemistry further showed that LPS selectively induced c-Fos in a large subset of melanocortin 4 receptor-expressing neurons in the lateral parabrachial nucleus. Secondly, we used pharmacogenetics to stimulate the activity of AgRP neurons during the course of LPS-induced anorexia. In AgRP-Cre mice expressing the designer receptor hM3Dq-Gq only in AgRP neurons, the administration of the designer drug clozapine-N-oxide (CNO) induced robust food intake. Strikingly, CNO-mediated food intake was rapidly and completely blunted by the coadministration of LPS. Neuroanatomical experiments further indicated that LPS did not interfere with the ability of CNO to stimulate c-Fos in AgRP neurons. In summary, our findings combined together support the view that the stimulation of select AgRP-innervated brain sites and target neurons, rather than the inhibition of AgRP neurons themselves, is likely to contribute to the rapid suppression of food intake observed during acute bacterial endotoxemia.

Dynamic and extensive metabolic state-dependent regulation of cytokine expression and circulating levels

Cytokines play diverse and critical roles in innate and acquired immunity, and several function within the central nervous system and in peripheral tissues to modulate energy metabolism. The extent to which changes in energy balance impact the expression and circulating levels of cytokines (many of which have pleiotropic functions) has not been systematically examined. To investigate metabolism-related changes in cytokine profiles, we used a multiplex approach to assess changes in 71 circulating mouse cytokines in response to acute (fasting and refeeding) and chronic (high-fat feeding) alterations in whole body metabolism. Refeeding significantly decreased serum levels of IL-22, IL-1α, soluble (s)IL-2Rα, and soluble vascular endothelial growth factor receptor 3 (VEGFR3), but markedly increased granulocyte colony-stimulating factor (G-CSF), IL-1β, chemokine (C-C motif) ligand (CCL2), sIL-1RI, lipocalin-2, pentraxin-3, tissue inhibitor of metalloproteinase (TIMP-1), and serum amyloid protein (SAP) relative to the fasted state. Interestingly, only a few of these changes paralleled the alterations in expression of their corresponding mRNAs. Functional studies demonstrated that central delivery of G-CSF increased, whereas IL-22 decreased, food intake. Changes in food intake were not accompanied by acute alterations in orexigenic (Npy and Agrp) and anorexigenic (Pomc and Cart) neuropeptide gene expression in the hypothalamus. In the context of chronic high-fat feeding, circulating levels of chemokine (C-X-C) ligand (CXCL1), serum amyloid protein A3 (SAA3), TIMP-1, α1-acid glycoprotein (AGP), and A2M were increased, whereas IL-12p40, CCL4, sCD30, soluble receptor for advanced glycation end products (sRAGE), CCL12, CCL20, CX3CL1, IL-16, IL-22, and haptoglobin were decreased relative to mice fed a control low-fat diet. These results demonstrate that both short- and long-term changes in whole body metabolism extensively alter cytokine expression and circulating levels, thus providing a foundation and framework for further investigations to ascertain the metabolic roles for these molecules in physiological and pathological states.

JAK-STAT and feeding

The regulation of energy balance requires a complex system to homeostatically maintain the adult body at a precise set point. The central nervous system, particularly the hypothalamus, plays a key role in integrating a variety of signals that can relay information about the body's energy stores. As part of this system, numerous cytokines and hormones contribute to the regulation of food intake and energy homeostasis. Cytokines, and some hormones, are known to act through JAK-STAT intracellular signaling pathways. The hormone leptin, which plays a vital role in appetite regulation, signals through the JAK-STAT pathway, and it is through this involvement that the JAK-STAT pathway has become an established component in the mechanisms regulating food intake within the body. Emerging research, however, is now showing that this involvement of JAK-STAT is not limited to its activation by leptin. Furthermore, while the JAK-STAT pathway may simply act to transmit the anorectic signal of circulating factors, this intracellular signaling pathway may also become impaired when normal regulation of energy balance is disrupted. Thus, altered JAK-STAT signaling may contribute to the breakdown of the normal homeostatic mechanisms maintaining body weight in obesity.

The endocrinology of food intake

Many questions must be considered with regard to consuming food, including when to eat, what to eat and how much to eat. Although eating is often thought to be a homeostatic behaviour, little evidence exists to suggest that eating is an automatic response to an acute shortage of energy. Instead, food intake can be considered as an integrated response over a prolonged period of time that maintains the levels of energy stored in adipocytes. When we eat is generally determined by habit, convenience or opportunity rather than need, and meals are preceded by a neurally-controlled coordinated secretion of numerous hormones that prime the digestive system for the anticipated caloric load. How much we eat is determined by satiation hormones that are secreted in response to ingested nutrients, and these signals are in turn modified by adiposity hormones that indicate the fat content of the body. In addition, many nonhomeostatic factors, including stress, learning, palatability and social influences, interact with other controllers of food intake. If a choice of food is available, what we eat is based on pleasure and past experience. This article reviews the hormones that mediate and influence these processes.

Chikuyou-Sekkou-To, a Traditional Chinese Herbal Medicine, Modulates Eating Behavior and Thermal Response Induced by Tumor Necrosis Factor-α in Rats

We investigated the effects of Chikuyou-Sekkou-To (TJS-167), a traditional Chinese herbal medicine, on changes in eating behavior and rectal temperature induced by administration of tumor necrosis factor-α ( TNF -α) in rats. Infusion of TNF -α into the third cerebral ventricle in doses of 1 to 4 μg/rat suppressed 24-hour cumulative food and water intake dose-dependently, compared to an infusion of phosphate-buffered saline (PBS) (p < 0.05 for each). The infusion of 2 μg/rat TNF -α into the third cerebral ventricle elevated rectal temperature compared to PBS controls (p < 0.05). In rats fed diets containing TJS-167 (1.38 g/kg/day) for 1 week, the suppressive effect of TNF -α (2 μg/rat) on food intake was alleviated significantly, compared to rats fed a standard diet (p < 0.05). The elevation of rectal temperature induced by TNF -α was attenuated significantly in the TJS-167-treated group compared to the control (p < 0.05). These results indicate that oral administration of TJS-167 may be effective in preventing or reducing TNF -α-induced inflammatory responses, such as appetite loss and elevation of body temperature.

Role of Lactobacillus acidophilus loaded floating beads in chronic fatigue syndrome: behavioral and biochemical evidences

BACKGROUND

  In recent years the interface between neuropsychiatry and gastroenterology has converged in to a new discipline referred to as enteric neuroscience. Implications of brain-gut communication in the pathogenesis of psychiatric disorders indicate a possible role of suitably packaged/delivered probiotics as newer therapeutic options. In the present study probable role of per-oral administration of free Lactobacillus acidophilus (LAB) and LAB loaded alginate beads in attenuation of the symptoms associated with chronic fatigue syndrome (CFS) were evaluated.

METHODS

  Chronic fatigue syndrome following physical fatigue was induced in rats by forcing them to swim (forced swim test; FST) in water till exhaustion, after weighing them down with 10% their body weight, daily for 28 days. Immobility (I) and postswim fatigue time (PSF) were taken as suitable markers. Free LAB and LAB loaded floating beads (FBs) were administered, from 21 to 28 days.

KEY RESULTS

  Immobility and PSF were found to increase considerably in FST rats (665 ± 22 s and 196 ± 6 s) as compared with the naïve (32 ± 7 s and 22 ± 2 s) at 20 days, establishing severe fatigue like behavior. FST control group exhibited significant (P < 0.05) hypertrophy of spleen, hypotrophy of thymus, and increased oxido-nitrosative stress in brain and tumor necrosis factor-α (TNF-α) levels in serum. Treatment with LAB and LAB FBs significantly decreased I and PSF and attenuated (P < 0.05) oxido-nitrosative stress and TNF-α levels. Spleen and thymus were also restored to their original size in this group.

CONCLUSIONS & INFERENCES

  The findings suggest a valuable therapeutic role of LAB especially when incorporated into alginate beads for the treatment of CFS.

Repletion of TNFα or leptin in calorically restricted mice suppresses post-restriction hyperphagia

The causes of post-restriction hyperphagia (PRH) represent a target for drug-based therapies to prevent obesity. However, the factors causing PRH are poorly understood. We show that, in mice, the extent of PRH was independent of the time under restriction, but depended on its severity, suggesting that PRH was driven by signals from altered body composition. Signals related to fat mass were important drivers. Circulating levels of leptin and TNFα were significantly depleted following caloric restriction (CR). We experimentally repleted their levels to match those of controls, and found that in both treatment groups the level of PRH was significantly blunted. These data establish a role for TNFα and leptin in the non-pathological regulation of energy homeostasis. Signals from adipose tissue, including but not limited to leptin and TNFα, regulate PRH and might be targets for therapies that support people engaged in CR to reduce obesity.

CNS leptin and insulin action in the control of energy homeostasis

The obesity and diabetes pandemics have made it an urgent necessity to define the central nervous system (CNS) pathways controlling body weight, energy expenditure, and fuel metabolism. The pancreatic hormone insulin and the adipose tissue-derived leptin are known to act on diverse neuronal circuits in the CNS to maintain body weight and metabolism in a variety of species, including humans. Because these homeostatic circuits are disrupted during the development of obesity, the pathomechanisms leading to CNS leptin and insulin resistance are a focal point of research. In this review, we summarize the recent findings concerning the mechanisms and novel neuronal mediators of both insulin and leptin action in the CNS.

Neurobiology of inflammation-associated anorexia

Compelling data demonstrate that inflammation-associated anorexia directly results from the action of pro-inflammatory factors, primarily cytokines and prostaglandins E2, on the nervous system. For instance, the aforementioned pro-inflammatory factors can stimulate the activity of peripheral sensory neurons, and induce their own de novo synthesis and release into the brain parenchyma and cerebrospinal fluid. Ultimately, it results in the mobilization of a specific neural circuit that shuts down appetite. The present article describes the different cell groups and neurotransmitters involved in inflammation-associated anorexia and examines how they interact with neural systems regulating feeding such as the melanocortin system. A better understanding of the neurobiological mechanisms underlying inflammation-associated anorexia will help to develop appetite stimulants for cancer and AIDS patients.

Prostaglandins and sickness behavior: old story, new insights

Previous evidence has shown that prostaglandins play a key role in the development of sickness behavior observed during inflammatory states. In particular, prostaglandin E2 (PGE2) is produced in the brain by a variety of inflammatory signals such as endotoxins or cytokines. Its injection has been also shown to induce symptoms of sickness behavior. The role of cyclooxygenase enzymes (COX), the rate-limiting enzymes converting arachidonic acid into prostaglandins, in sickness behavior has been extensively studied, and it has been demonstrated that strategies aiming at inhibiting these enzymes limit anorexia, body weight loss and fever in animals with inflammatory diseases. However, inhibiting COX activity may lead to negative gastric or cardiovascular effects, since COX enzymes play a role in the synthesis of others prostanoids with various and sometimes contrasting properties. Recently, prostaglandin E synthases (PGES), which specifically catalyze the final step of PGE2 biosynthesis, were characterized. Among these enzymes, the microsomal prostaglandin E synthase-1 (mPGES-1) was of a particular interest since it was shown to be up-regulated by inflammatory signals in a variety of cell types. Moreover, mPGES-1 was shown to be crucial for correct immune-to-brain communication and induction of fever and anorexia by pro-inflammatory agents. This review takes stock of previous knowledge and recent advances in understanding the role of prostaglandins and of their specific synthesizing enzymes in the molecular mechanisms underlying sickness behavior. The review concludes with a short summary of key questions that remain to be addressed and points out therapeutic developments in this research field.

Involvement of stomach ghrelin and hypothalamic neuropeptides in tumor necrosis factor-alpha-induced hypophagia in mice

This study aimed to clarify the interaction of tumor necrosis factor-alpha (TNF-alpha), an anorexigenic cytokine, with ghrelin, an orexigenic peptide secreted by the stomach lining, and hypothalamic neuropeptides in the regulation of food intake in mice. The peripheral administration of TNF-alpha dose-dependently decreased the 24-h cumulative food intake compared with the administration of saline. Reduced food intake was observed at 6 h and 24 h. The same TNF-alpha treatment significantly decreased the plasma level of ghrelin at 6 h and 24 h after treatment compared with the control levels. These changes were accompanied by a significant reduction in the expression of ghrelin mRNA in the stomach at 24 h after treatment. TNF-alpha treatment also resulted in a significant increase in expression of pro-opiomelanocortin (POMC) mRNA and a significant decrease in expression of agouti-related protein (AGRP) mRNA in the hypothalamus at 6 h after treatment. Finally, the pre-administration of ghrelin, reversed the TNF-alpha-induced hypophagia in mice at 6 and 24 h. Taken together, these findings suggest that hypothalamic POMC and AGRP and stomach ghrelin may be involved in TNF-alpha-induced hypophagia in mice.

Intracerebroventricular infusions of gp120 inhibit weight gain and induce atrophy in the hippocampus and neostriatum without affecting cognition

The HIV envelope protein, gp120, has been proposed to be a key agent in the development of AIDS dementia complex (ADC). To elucidate CNS effects that gp120 alone may be inducing in ADC, the present study investigated changes in weight, motor activity, cognitive function and corresponding neuropathology in rats given daily bilateral infusions of gp120 intracerebroventricularly for 7 days. gp120 inhibited weight gain, but had no measurable effects on motor activity or water maze cognitive performance. Nonetheless, gp120 infusions did induce both hippocampal and neostriatal atrophy. Thus, gp120 alone can cause ADC-related neuropathologic and weight changes, but gp120 alone was not sufficient to induce impairments in spatial learning and memory.

Green tea (Camellia sinensis) extract ameliorates endotoxin induced sickness behavior and liver damage in rats

Immune activation, either by cytokines or endotoxin, elicits a constellation of nonspecific symptoms such as weakness, malaise, listlessness, fatigue, adipsia, anorexia, depression and anxiety collectively termed as sickness behavior. Further, endotoxin administration in animals has been implicated in the pathogenesis of many types of liver disease. Green tea, a common household drink, is rich in antioxidant polyphenols demonstrating inhibitory effects on cytokine production. The present study was designed to investigate the effect of chronic treatment of green tea extract (GTE) on lipopolysaccharide (LPS)-induced sickness behavior and liver damage in rats. The hypothesis was tested through the analysis of LPS-induced behavioral changes in rats, in plus maze and open field paradigms. Other parameters such as feeding and water consumption, weight loss and organ weight index were also estimated. Liver function tests were conducted to investigate the effect of GTE supplementation on LPS-induced hepatic dysfunction. The results of the study demonstrated that GTE significantly attenuated LPS-induced sickness behavior as well as hepatic damage either by its antioxidant activity or by inhibiting LPS induced cytokine production in rats.

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.

Diabetic patients can do as well on peritoneal dialysis as nondiabetic patients

BACKGROUND

It is not uncommon that diabetic peritoneal dialysis (PD) patients are volume overloaded and this may have contributed to the inferior outcome of diabetic patients. In the present cohort study, we compared the difference between diabetics and nondiabetics during the first year of PD after implementing strict volume control.

METHODS

Seventeen diabetic and 40 nondiabetic incident PD patients were followed for 1 year. Fluid status was evaluated by bioimpedance analysis and blood pressure. Nutritional status was evaluated by subjective global nutritional assessment.

RESULTS

At the initiation, compared with the nondiabetics, diabetics had a significantly higher extracelluar volume, systolic blood pressure and lower serum albumin. One year later, there were no statistical differences in these parameters between the two groups. The prevalence of malnutrition decreased in all patients, although malnutrition remained slightly higher in diabetic patients.

CONCLUSIONS

Our study suggests that diabetics can do as well as nondiabetics on PD. Appropriate diabetic care, especially strict volume control, may be critical for the success of diabetic patients on PD treatment.

Strong Association Between Volume Status and Nutritional Status in Peritoneal Dialysis Patients

BACKGROUND

Malnutrition is a strong predictor of mortality in maintenance peritoneal dialysis (PD) patients. Various factors have been identified to contribute to the development of malnutrition. The present study tried to investigate the possible role of fluid overload in the development of malnutrition.

METHODS

Twenty-eight PD patients were included in this study. Fluid status was evaluated by means of repeated bioimpedance analysis, and nutritional status was assessed by means of handgrip strength and subjective global assessment. All patients were followed up closely for 9 months. Based on changes in bioimpedance analysis data, patients were divided into group A (with continuous and steadily improved fluid status; n = 18) and group B (with consistent fluid overload; n = 10).

RESULTS

There were no differences in sex, age, and height between the 2 groups. In group A, patients' extracellular water (ECW) volume decreased significantly during follow-up, whereas intracellular water (ICW) volume increased significantly (both P < 0.001). In group B, ECW volume increased significantly, whereas ICW volume increased at an early stage and then decreased. The ratio of ECW to total-body water decreased significantly in group A, but increased significantly in group B. Along with the improvement in fluid status, nutritional status in group A also improved significantly (the prevalence of malnutrition decreased from 66.7% to 11.1%; P < 0.01). However, in group B, nutritional status deteriorated significantly (handgrip strength decreased from 238.33 +/- 88.93 to 216.1 +/- 86.19 N; P < 0.05; and the prevalence of malnutrition increased from 40% to 50%).

CONCLUSION

Our data suggest there is a strong association between fluid status and nutritional status. Improved fluid status is associated with improvement in nutritional status, whereas deterioration in fluid status is associated with the development of malnutrition.

Effect of short-term cigarette smoke exposure on body weight, appetite and brain neuropeptide Y in mice

Although nicotinic receptors have been demonstrated in hypothalamic appetite-regulating areas and nicotine administration alters food intake and body weight in both animals and humans, the mechanisms underlying the effects of smoking on appetite circuits remain unclear. Conflicting effects of nicotine on the major orexigenic peptide, neuropeptide Y (NPY), have been observed in the brain, but the effects of smoking are unknown. Thus, we aimed to investigate how cigarette smoking affects body weight, food intake, plasma leptin concentration, hypothalamic NPY peptide, adipose mass and mRNA expression of uncoupling proteins (UCP), and tumor necrosis factor (TNF) alpha. Balb/C mice (8 weeks) were exposed to cigarette smoke (three cigarettes, three times a day for 4 consecutive days) or sham exposed. Body weight and food intake were recorded. Plasma leptin and brain NPY were measured by radioimmunoassay. UCPs and TNF alpha mRNA were measured by real-time PCR. Food intake dropped significantly from the first day of smoking, and weight loss became evident within 2 days. Brown fat and retroperitoneal white fat masses were significantly reduced, and plasma leptin concentration was decreased by 34%, in line with the decreased fat mass. NPY concentrations in hypothalamic subregions were similar between two groups. UCP1 mRNA was decreased in white fat and UCP3 mRNA increased in brown fat in smoking group. Short-term cigarette smoke exposure led to reduced body weight, food intake, and fat mass. The reduction in plasma leptin concentration may have been too modest to increase NPY production; alternatively, change in NPY or its function might have been offset by nicotine or other elements in cigarette smoke.

TNF-α and intPLA2 genes' polymorphism in anorexia nervosa

OBJECTIVE

The aim of this study was the assessment of -308G/A tumor necrosis factor (TNF)-α gene polymorphism and intPLA2 gene polymorphism in patients with anorexia nervosa (AN) and healthy controls.

SUBJECTS

We studied 91 non-related patients with AN and 144 healthy women (blood donors and students). The mean age of women from study group was 18.22 years (SD ± 3.13 years) and from control group was 31.71 years (SD ± 8.22).

METHODS

Gene polymorphisms were studied with the use of polymerase chain reaction-restriction fragment length polymorphism method. TNF-α gene polymorphism consists of G/A substitution in -308 promoter region. IntPLA2 gene polymorphism is related to intron 1, in which restrictive region is found and recognized by BanI enzyme.

RESULTS

We did not obtain statistically significant differences in the frequency of genotypes and alleles of -308G/A TNF-α polymorphism between the study and control groups (genotypes: P = 0.106, alleles: P = 0.076). We did analogous analysis in the restrictive and bulimic subgroups. We did not observe statistically relevant differences in the frequency of genotypes (P = 0.700) and alleles (P = 0.305). We did not obtain statistically relevant difference in the frequency of genotypes and alleles of intPLA2 gene between the study group and controls (genotypes: P = 0.300, alleles: P = 0.331). We did analogous analysis in both subgroups of AN. We did not observe statistically relevant differences in the frequency of genotypes (P = 0.344) and alleles (P = 0.230).

CONCLUSIONS

There was no statistically relevant trend for the association between TNF-α polymorphism and AN. We did not find association between studied polymorphism of intPLA2 gene and risk of AN.

Influence of membrane-bound tumor necrosis factor (TNF)-alpha on obesity and glucose metabolism

OBJECTIVES

To investigate the influence of transmembrane tumor necrosis factor (TNF)-alpha on adipose tissue development and insulin-mediated glucose metabolism.

METHODS AND RESULTS

TNF-alpha and lymphotoxin-alpha-deficient mice expressing non-cleavable transmembrane TNF-alpha (Tg-tmTNF-alpha) and TNF-alpha/lymphotoxin-alpha double knockout (control) mice were kept on high-fat diet for 15 weeks. The food intake and feeding efficiency of Tg-tmTNF-alpha mice were significantly higher compared with control mice. At the end of the study, Tg-tmTNF-alpha mice had a significantly higher total body weight, as well as subcutaneous and gonadal adipose tissue mass. Histological analysis revealed that the expression of Tg-tmTNF-alpha resulted in a significantly increased adipocyte area and blood vessel density. Plasma leptin levels correlated positively with adipose tissue mass. The plasma levels of total cholesterol and HDL-cholesterol were significantly increased and LDL-cholesterol levels significantly decreased in Tg-tmTNF-alpha mice. Fasting blood glucose and plasma insulin levels were not different between the two genotypes and intraperitoneal glucose and insulin tolerance tests did not show significant differences.

CONCLUSIONS

Transmembrane TNF-alpha enhances adipose tissue formation without altering insulin-mediated glucose metabolism in mice with nutritionally induced obesity.

Leptin, tumor necrosis factor-α (TNF), and CD14 in ovine adipose tissue and changes in circulating TNF in lean and fat sheep2

Four studies were designed to determine whether 1) tumor necrosis factor-alpha (TNF) and the Lipopolysaccharide (LPS) binding ligand, CD14, are produced by sheep adipose tissue; 2) nutritional reserves and/or short-term fasting affect circulating concentrations of TNF; 3) there is a relationship between TNF and metabolic factors in sheep; and 4) inflammation alters circulating concentrations of leptin. In Exp. 1 and 2, ewes were assigned, based on ultrasonic assessments of last-rib subcutaneous fat measurements to fat (fat thickness > 1 cm; mean = 1.52 +/- 0.03 cm) or thin (fat thickness < 1 cm; mean = 0.25 +/- 0.03 cm) groups. Fat and thin ewes were assigned to fed or fasted groups for a total of four groups (fed-fat; fasted-fat; fed-thin; fasted-thin). Fed-ewes had ad libitum access to feed, and fasted-ewes were prohibited feed 48 h before initiation of sample collection. In Exp. 1, subcutaneous fat samples were collected from just above the last rib for detection of TNF and CD14 mRNA, and immunoreactivity. Tumor necrosis factor-alpha-like immunoreactivity in adipocytes was sparse, more pronounced in cells in fed-ewes than fasted-ewes, and localized to membranes between adjacent cells in nucleated regions. Immunoreactivity for CD14 was minimally observed but present in adipocytes and widely expressed in infiltrating monocytes and epithelial vascular cells. Leptin was detected in adipocytes. In Exp. 2, plasma samples collected every 6 h for 24 h were analyzed for plasma concentrations of TNF. Fat ewes had greater plasma concentrations of TNF than thin ewes (P = 0.039). In Exp. 3, wethers were injected i.v. with interleukin-1beta or TNF. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not affected by treatment (P > 0.39). In Exp. 4, wethers were injected with LPS. Blood samples were collected every 15 min for 8 h following injection. Plasma concentration of leptin was not altered by LPS (P > 0.20). These results provide evidence: 1) of TNF-like immunoreactivity within fat tissue; 2) that elements within fatty tissues have CD14 that may allow adipocyte function to be directly affected by LPS; 3) that plasma concentrations of leptin are not altered by LPS treatment; and 4) that circulating concentrations of TNF are elevated with obesity in sheep.

Decreased orexigenic response to neuropeptide Y in rats with obstructive cholestasis

Neuropeptide Y (NPY) is a key factor in the neurochemical control of food intake, and obstructive cholestasis can be associated with disturbances in food intake. Our aim in this study was to determine whether obstructive cholestasis in the rat is associated with defective central responsiveness to NPY. Cholestasis was induced in rats by surgical bile duct resection. Rats with obstructive cholestasis exhibited a 20% reduction in food intake 2 days after laparotomy (compared with sham-resected controls) that had resolved by 4 days after surgery. Responsiveness to the orexigenic action of NPY was tested by measuring food intake after intracerebroventricular injection of NPY. In sham-resected rats, NPY infusion strikingly increased food intake, whereas bile duct-resected (BDR) rats showed a consistent significantly impaired feeding response to NPY at postlaparotomy days 2, 4, and 7. Separate experiments measured specific binding of [(3)H]NPY to hypothalamic receptors. Fos protein expression was measured in the hypothalamic paraventricular nucleus (PVN) as a marker of NPY-induced neuronal activation. The decreased orexigenic responsiveness to NPY was not caused by altered NPY binding at hypothalamic receptors or its ability to activate neurons in the PVN. Therefore, cholestatic rats demonstrate an attenuated NPY-induced orexigenic drive that occurs early after biliary obstruction, when cholestatic rats exhibit reduced food intake, and persists despite the return of food intake to normal levels and the presence of intact central NPY-related neuronal pathways.

Maternal undernutrition induces neuroendocrine immune dysfunction in male pups at weaning

The present study was designed to assess the effect of maternal undernutrition, during gestation and lactation, on the neuroendocrine [hypothalamo-pituitary-adrenal (HPA)]-immune axis response to endotoxin (LPS) administration. For this purpose, 21-day-old male rats from both well-nourished (WN) and undernourished (UN) mothers were examined 2 h after injection (i.p.) of vehicle alone (VEH) or containing LPS (130 microg/kg BW). Circulating levels of glucose (GLU), ACTH, corticosterone (B), tumor necrosis factor-alpha (TNFalpha) and leptin were explored. The results indicate that: (a) mother body weight was significantly (p < 0.05) reduced, as a consequence of UN, at the second and third weeks of pregnancy; (b) no differences in basal glycemia were found in the two groups of pups, and LPS treatment did not induce hypoglycemia, in either group; (c) basal plasma ACTH, B and TNFalpha levels were similar in the two groups, and LPS-induced ACTH, B and TNFalpha secretions, although severalfold higher than respective VEH values (p < 0.05) in pups from WN mothers, were fully (ACTH and B) and partially (TNFalpha) abolished in products from UN mothers; (d) both mean body weights and basal plasma leptin levels were significantly (p < 0.05) lower in pups from UN than from WN mothers, and LPS administration did not modify plasma leptin values in products from both groups. In addition, results of dispersed total adrenal cells incubated in vitro indicate that: (a) both basal and ACTH (22 pM)-induced B secretion were significantly (p < 0.05) lower in cells from UN than WN pups, and (b) leptin (100 nM) was able to inhibit partially ACTH-stimulated B output by adrenal gland (AG) cells from WN pups; however, it failed to inhibit ACTH-stimulated glucocorticoid release by AG cells from UN pups. The present results indicate that undernutrition in mothers, during the very critical periods of gestation and lactation, induces in their male pups at weaning: (a) reduced circulating leptin levels and body weight values; (b) metabolic adaptation to normal carbohydrate metabolism; (c) hyporesponsiveness of the HPA and immune (TNFalpha) axes during endotoxemia, and (d) leptin resistance at the adrenocortical level. This study strongly supports that undernutrition of mothers results in neuroendocrine immune dysfunction of their pups; however, adrenal resistance to the inhibitory effect of leptin on glucocorticoid output is developed, probably as an adaptive mechanism to counteract unfavorable metabolic conditions.

Learning performances, brain NGF distribution and NPY levels in transgenic mice expressing TNF-alpha

Tumor necrosis factor-alpha (TNF-alpha) is a cytokine involved in a variety of neurobiological activities including changing behavior and regulation of both neurotrophin and neuropeptide levels. In this study we used two lines of transgenic mice overexpressing brain TNF-alpha characterized by neurological deficits (line Tg6074) or phenotypically normal (line TgK3). We analyzed whether or not impairments in learning and memory processes due to TNF-alpha overexpression were associated with changes in endogenous brain NGF, NPY and beta-amyloid. The results indicate that full TNF-alpha transgene expression disrupted the learning capabilities of transgenic mice (both Tg6074 and TgK3). NGF decreased in the hippocampus of both transgenic mice whereas hippocampal NPY slightly potentiated in Tg6074. The decrease in NGF is correlated with deficits in spatial learning and memory whereas inflammation in the brain of Tg6074 could be responsible of the hippocampal increase in NPY. As a whole, these results show that transgenic mice overexpressing TNF-alpha in the brain represent a useful model for studying neuronal degeneration and brain inflammatory processes.

Metabolic, neuroendocrine and immune functions in basal conditions and during the acute-phase response to endotoxic shock in undernourished rats

Chronic malnutrition is one of the most important causes of several metabolic, immune and neuroendocrine dysfunctions. The aim of the present study was to determine the influence of chronic food restriction on basal neuroendocrine, immune and adipocyte functions and during the acute-phase response to endotoxic shock in female rats. The effect of refeeding of undernourished rats on the above-mentioned functions was also investigated. For these purposes, plasma total protein, glucose, triglycerides, ACTH, corticosterone, tumor necrosis factor-alpha (TNF) and leptin (LEP) levels were determined in basal condition and 2 h after endotoxin (LPS; 180 microgram/kg body weight, i.p.) administration in 3 different groups: (1) well-nourished (WN) controls; (2) undernourished (UN) rats as a consequence of chronic food restriction, and (3) UN rats re-fed to restoration of their body weights in the WN rat range. The results indicate that UN rats, in comparison with WN controls, developed an arrest in body weight gain as well as in basal hypoglycemia, hypotriglyceridemia, hypoleptinemia, hypercorticosteronemia and enhanced adrenal glucocorticoid content; however, no changes in basal total protein, ACTH and TNF plasma levels and in anterior pituitary ACTH concentrations were found. When endotoxic shock was induced, the LPS-induced hypoglycemia developed in WN rats was abolished in UN animals, and both ACTH and TNF plasma concentrations after endotoxin, albeit significantly (p < 0.05) higher than the respective basal values, were significantly (p < 0.05) lower in UN than in WN control rats. Despite the high basal plasma corticosterone concentration in UN vs. WN rats, the LPS-induced glucocorticoid release was similar in WN and UN rats. Additionally, LPS treatment did not modify basal plasma LEP levels, regardless of the group. Interestingly, UN rats fed ad libitum for 15 days restored their body weight to WN rat range values, and the various metabolic dysfunctions seen in UN rats in both basal and post-LPS conditions were fully normalized. Our results clearly indicate that chronic undernutrition not only affects, as earlier described, reproductive function but also metabolic, neuroendocrine, immune and adipocyte functions, and that the effects induced by undernutrition can be fully reversed after recovery of normal body weight. The present study strongly supports the involvement of the metabolic status in the effectiveness of the defense mechanisms developed in patients in inflammatory stress conditions.

Use of recombinant human soluble TNF receptor in anorectic tumor-bearing rats

With progression of tumor growth, rats demonstrate anorexia and reduced food intake, a function of meal number and meal size. Tumor necrosis factor-alpha (TNF-alpha), a recognized anorectic agent, reacts with two different receptors (type I: 55 kDa; type II: 75 kDa). We used a dimeric, pegylated 55-kDa TNF receptor construct to test its effects on food intake, meal number, and meal size, which were continuously measured with a rat eater meter in 16 Fischer 344 male rats injected with 10(6) viable methylcholanthrene cells. When anorexia developed, rats received a subcutaneous injection of either 0.25 mg/kg body wt of soluble TNF receptor construct (study) or vehicle (tumor-bearing control). Before TNF inhibitor injection, no differences were observed in food intake, meal number, or meal size between the two groups. After the TNF inhibitor injection, study vs. control rats significantly improved food intake as a result of an increase in meal number and meal size. Rats also showed a significant improvement in body weight. These data suggest that TNF-alpha, in addition to other cytokines, contributes to the anorexia of tumor growth, probably mediated via the hypothalamus.

Role of glucocorticoids in the response of the hypothalamo-corticotrope, immune and adipose systems to repeated endotoxin administration

The present study was designed to determine whether the glucocorticoid inhibitory feedback mechanism plays a role in the well-known tolerance of the neuroendocrine-immune axis response to repeated endotoxemia. Adult male rats underwent adrenalectomy (ADX) and were implanted with a subcutaneous corticosterone (compound B, CB, 75 mg) pellet, or sham operated and implanted with a placebo pellet. On the morning of day 8 after surgery (experimental day, D1), all rats received an intravenous injection of lipopolysaccharide (LPS) (25 microg/kg body weight) which was repeated daily until D5. Blood was drawn via intravenous indwelling catheters before (sample time zero) as well as 1, 2, 3 and 4 h after LPS treatment on D1, 3 and 5 for measurements of corticotropin (ACTH), CB, tumor necrosis factor-alpha (TNF-alpha) and leptin. In sham animals, tolerance to repeated LPS administration was complete by D5 for the corticotrope axis and the immune response. In addition, LPS was found to stimulate leptin secretion on day 1 in intact rats, an effect that also disappeared thereafter. ADX + CB rats showed only a partial tolerance of the corticotrope axis on D5, whereas tolerance of the immune response was similar to that found in sham animals. Interestingly, the acute stimulation of leptin secretion by LPS in ADX + CB rats was qualitatively similar to that of intact controls on D1, but plasma leptin levels were significantly reduced on D3 and 5 compared to controls. Our results demonstrate that the adrenal response tolerance of the hypothalamo-pituitary-adrenal axis to repeated endotoxemia. In addition, our finding that TNF-alpha secretion follows the same pattern in sham-operated and in adrenalectomized animals suggests that unlike the corticotrope axis, tolerance of the immune response does not depend upon stimulated CB levels. The decrease in circulating levels of leptin following ADX is consistent with the stimulatory effects of glucocorticoids on leptin secretion. However, our finding of an acute stimulation of leptin secretion by LPS in ADX + CB animals demonstrates that this effect of endotoxemia is at least partially glucocorticoid independent.

Induction of rat uncoupling protein-2 gene treated with tumour necrosis factor alpha in vivo

BACKGROUND

The cytokine tumour necrosis factor (TNF) alpha has been reported to induce metabolic abnormalities such as anorexia and thermogenesis. To investigate functional modulators of uncoupling protein-2 (UCP2) gene expression, we examined the effects of TNF-alpha on UCP2 mRNA expression in rats.

METHODS

Mature male Wistar King A (WKA) rats at 10-11 weeks of age were treated with recombinant human TNF-alpha at a dose of 0.6 nmol 100 g-1 body weight by intraperitoneal administration.

RESULTS

TNF-alpha treatment induced an increase in UCP2 mRNA expression in broadly distributed tissues including brown adipose tissue (BAT), white adipose tissue (WAT) and skeletal muscle, and an elevation of ob gene mRNA expression in WAT. After the TNF-alpha treatment, an increase in plasma leptin concentration occurred in an ob gene-dependent manner, accompanied by an anorectic effect.

CONCLUSION

The present results provide evidence for a new regulatory loop involving TNF-alpha and UCP2, and add novel insights into the regulatory mechanisms of energy homeostasis.

Effect of providing fortified meals and between-meal snacks on energy and protein intake of hospital patients

This study aimed to evaluate whether food fortification and snacks could increase the energy and protein intakes of hospital patients. The control group of 82 consecutive admissions on medical, elderly care and orthopaedic wards ate freely from the hospital menu. Subsequently, an intervention group of 62 patients were offered fortified food and snacks, providing an extra 22.2|g protein/day and 966 kcal/day in addition to the standard menu. Fortification significantly increased energy intake in the intervention group (P = 0.007, independent samples t-test), having the greatest effect on groups with the lowest energy intake, that is male and female orthopaedic, female medical and female elderly patients (84 cent of total). The increases in energy intake were 21.3 cent, 21.4 cent, 23 cent and 19.6 cent respectively. Although the increased energy and protein intake represented 25.6 cent and 22.5 cent respectively, of the supplements given, and suggested that wastage was high, it was nevertheless sufficient to remove energy deficit. We therefore propose that provision of fortified food and snacks is a convenient method of improving the nutritional intakes of hospital patients.

Measuring reward with the conditioned place preference paradigm: a comprehensive review of drug effects, recent progress and new issues

This review gives an overview of recent findings and developments in research on brain mechanisms of reward and reinforcement from studies using the place preference conditioning paradigm, with emphasis on those studies that have been published within the last decade. Methodological issues of the paradigm (such as design of the conditioning apparatus, biased vs unbiased conditioning, state dependency effects) are discussed. Results from studies using systemic and local (intracranial) drug administration, natural reinforcers, and non-drug treatments and from studies examining the effects of lesions are presented. Papers reporting on conditioned place aversion (CPA) experiments are also included. A special emphasis is put on the issue of tolerance and sensitization to the rewarding properties of drugs. Transmitter systems that have been investigated with respect to their involvement in brain reward mechanisms include dopamine, opioids, acetylcholine, GABA, serotonin, glutamate, substance P, and cholecystokinin, the motivational significance of which has been examined either directly, by using respective agonist or antagonist drugs, or indirectly, by studying the effects of these drugs on the reward induced by other drugs. For a number of these transmitters, detailed studies have been conducted to delineate the receptor subtype(s) responsible for the mediation of the observed drug effects, particularly in the case of dopamine, the opioids, serotonin and glutamate. Brain sites that have been implicated in the mediation of drug-induced place conditioning include the 'traditional' brain reward sites, ventral tegmental area and nucleus accumbens, but the medial prefrontal cortex, ventral pallidum, amygdala and the pedunculopontine tegmental nucleus have also been shown to play important roles in the mediation of place conditioning induced by drugs or natural reinforcers. Thus, although the paradigm has also been criticized because of some inherent methodological problems, it is clear that during the past decade place preference conditioning has become a valuable and firmly established and very widely used tool in behavioural pharmacology and addiction research.

Interleukin-1beta-converting enzyme-deficient mice resist central but not systemic endotoxin-induced anorexia

Interleukin-1beta (IL-1beta) mediates many of the behavioral responses to infection and inflammation, and IL-1beta-converting enzyme (ICE) processes intracellular IL-1beta, leading to its maturation and secretion. Here we demonstrate that intracerebroventricular injections of lipopolysaccharide (LPS) produced a greater reduction in both food intake and food-motivated behavior in wild-type compared with ICE-deficient (ICE -/-) mice. This defect occurred although ICE -/- mice were able to fully respond to intracerebroventricular injections of IL-1beta. In contrast, ICE -/- mice remained fully responsive to intraperitoneal injections of LPS. These results indicate that brain, but not peripheral, IL-1beta plays a critical role in the depression in food intake that occurs during inflammation.

Exploratory and displacement behavior in transgenic mice expressing high levels of brain TNF-alpha

Studies reported recently have shown that tumor necrosis factor-alpha (TNF-alpha) a cytokine released by macrophages and monocytes plays a key role in inflammatory processes and immune and neuro-endocrine regulation. TNF-alpha is also produced in the central nervous system (CNS). However, the role of this cytokine in the CNS is largely unknown, although evidence indicates that it is involved in various neurobehavioral manifestations. Using transgenic mice expressing high amounts of murine TNF-alpha transgene in the neurons of the CNS, we investigated the stereotyped, exploratory, and displacement activities in the hole-board and black/white box. Transgenic mice and their normal control littermates were hybrids of the CBA x C57BL/6 genetic backgrounds and were obtained by backcrossing the CBA x C57BL/6 founder female and her progeny with F1 hybrid mates. Transgenic mice did not show changes in the stereotyped behavior on the hole-board, but they displayed several alterations in the exploratory activities both in the hole-board and black/white box. Transgenic mice also exhibited an increase in grooming when exposed to a highly unfamiliar environmental stimuli in the black/white box. The study suggests that supranormal endogenous TNF-alpha in the brain affects the behavioral responses to stressful conditions.

The role of cytokines in the behavioral responses to endotoxin and influenza virus infection in mice: effects of acute and chronic administration of the interleukin-1-receptor antagonist (IL-1ra)

Following infection with influenza virus, animals display decreased locomotor activity and feeding behavior and loss of body weight. It has been suggested that these effects may be mediated by cytokines, such as interleukin-1 (IL-1), interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-alpha), induced by the infection. To assess the potential role of IL-1, we tested the ability of a naturally occurring IL-1-receptor antagonist (IL-1ra) to antagonize the changes in feeding behavior induced by IL-1, endotoxin (lipopolysaccharide, LPS), and infection with influenza virus. Feeding behavior was assessed by measuring the daily intake of food pellets and sweetened milk in a 30-min period. Acute injection of IL-1 beta decreased milk intake, but mouse IL-6 and mouse TNF-alpha did not. However, TNF-alpha decreased food pellet intake slightly, especially when it was injected at the beginning of the dark phase. The reductions in milk intake induced by mouse IL-1 beta were largely prevented by IL-1ra pretreatment (100 micrograms/mouse i.p.). The LPS-induced reductions in milk intake were attenuated, but not blocked, by IL-1ra treatment (300 micrograms/mouse). LPS still induced significant decrements in the presence of the antagonist. In influenza virus-infected mice, IL-1ra was administered either by repeated subcutaneous (s.c.) injections, or by continuous s.c. infusion from osmotic minipumps. These IL-1ra treatments produced small, but statistically significant, attenuations of the depression in milk and food pellet intake in the virus-infected mice. In several experiments, IL-1ra treatment increased the survival of influenza virus-infected mice. Thus the attenuation of the hypophagia may have been caused by this IL-1ra-induced increase in survival. The results suggest that IL-1 contributes to sickness behavior induced by LPS and influenza virus infection, but it is not the only factor involved.

Malnutrition in HIV infection

Malnutrition is a common complication of HIV infection and plays a significant and independent role in morbidity and mortality. Many studies have been conducted to assess the appropriate role of nutrition in the clinical management of HIV infection. The complex nature of AIDS wasting, however, requires individualized strategies when providing nutritional support. Algorithms to assist in the diagnosis and treatment of malnutrition in HIV infection serve as general guidelines.