Long-term dynamics of serum α-MSH and α-MSH-binding immunoglobulins with a link to gut microbiota composition in patients with anorexia nervosa.

INTRODUCTION: Immunoglobulins (Ig) reactive with α-melanocyte-stimulating hormone (α-MSH), an anorexigenic neuropeptide, are present in humans and were previously associated with eating disorders. In this longitudinal study involving patients with anorexia nervosa (AN), we determined whether α-MSH in serum is bound to IgG and analyzed long-term dynamics of both α-MSH peptide and α-MSH-reactive Ig in relation to changes in BMI and gut microbiota composition. METHODS: The study included 64 adolescents with a restrictive form of AN, whose serum samples were collected at hospital admission, discharge, and during a 1-year follow-up visit, and 41 healthy controls, all females. RESULTS: We found that in both study groups, approximately 40% of serum α-MSH was reversibly bound to IgG and that levels of α-MSH-reactive IgG, but not of α-MSH peptide in patients with AN were low at hospital admission, but recovered 1-year later. Total IgG levels were also low at admission. Moreover, BMI-standard deviation score (SDS) correlated positively with α-MSH IgG in both groups studied, but negatively with α-MSH peptide only in controls. Significant correlations between the abundance of specific bacterial taxa in the gut microbiota and α-MSH peptide and IgG levels were found in both study groups, but they were more frequent in controls. CONCLUSION/DISCUSSION: We conclude that IgG in the blood plays a role as an α-MSH binding protein, whose characteristics are associated with BMI in both patients with AN and controls. Furthermore, the study suggests that low production of α-MSH-reactive IgG during the starvation phase in patients with AN may be related to altered gut microbiota composition.

Protein Extract of a Probiotic Strain of Hafnia alvei and Bacterial ClpB Protein Improve Glucose Tolerance in Mice.

A commercial strain of Hafnia alvei (H. alvei) 4597 bacteria was shown to reduce food intake and promote weight loss, effects possibly induced by the bacterial protein ClpB, an antigen-mimetic of the anorexigenic α-melanocyte-stimulating hormone. A decrease in the basal plasma glucose levels was also observed in overweight fasted humans and mice receiving H. alvei. However, it is not known whether H. alvei influences sweet taste preference and whether its protein extract or ClpB are sufficient to increase glucose tolerance; these are the objectives tested in the present study. C57BL/6J male mice were kept under standard diet and were gavaged daily for 17 days with a suspension of H. alvei (4.5 × 107 CFU/animal) or with H. alvei total protein extract (5 µg/animal) or saline as a control. Sweet taste preference was analyzed via a brief-access licking test with sucrose solution. Glucose tolerance tests (GTT) were performed after the intraperitoneal (IP) or intragastric (IG) glucose administration at the 9th and 15th days of gavage, respectively. The expression of regulatory peptides' mRNA levels was assayed in the hypothalamus. In another experiment performed in non-treated C57BL/6J male mice, effects of acute IP administration of recombinant ClpB protein on glucose tolerance were studied by both IP- and IG-GTT. Mice treated with the H. alvei protein extract showed an improved glucose tolerance in IP-GTT but not in IG-GTT. Both groups treated with H. alvei bacteria or protein extract showed a reduction of pancreatic tissue weight but without significant changes to basal plasma insulin. No significant effects of H. alvei bacteria or its total protein extract administration were observed on the sweet taste preference, insulin tolerance and expression of regulatory peptides' mRNA in the hypothalamus. Acute administration of ClpB in non-treated mice increased glucose tolerance during the IP-GTT but not the IG-GTT, and reduced basal plasma glucose levels. We conclude that both the H. alvei protein extract introduced orally and the ClpB protein administered via IP improve glucose tolerance probably by acting at the glucose postabsorptive level. Moreover, H. alvei probiotic does not seem to influence the sweet taste preference. These results justify future testing of both the H. alvei protein extract and ClpB protein in animal models of diabetes.

Lactobacillus salivarius and Lactobacillus gasseri supplementation reduces stress-induced sugar craving in mice.

OBJECTIVE: Increased intake of sweets or sugar craving may occur in response to chronic stress representing a risk factor for development of eating disorders and obesity. However, no safe treatment of stress-induced sugar craving is available. In this study we analysed effects of two Lactobacillus strains on food and sucrose intake in mice before and during their exposure to a chronic mild stress (CMS). RESEARCH METHODS & PROCEDURES: C57Bl6 mice were gavaged daily for 27 days with a mix of L. salivarius (LS) LS7892 and L. gasseri (LG) LG6410 strains or with 0.9% NaCl as a control. Following 10 days of gavage, mice were individually placed into the Modular Phenotypic cages, and after 7 days of acclimation were exposed to a CMS model for 10 days. Food, water and 2% sucrose intakes as well as meal pattern were monitored. Anxiety and depressive-like behaviour were analysed by standard tests. RESULTS: Exposure of mice to CMS was accompanied by increased size of sucrose intake in the control group likely reflecting the stress-induced sugar craving. A consistent, about 20% lower total sucrose intake, was observed in the Lactobacilli-treated group during stress which was mainly due to a reduced number of intakes. Lactobacilli treatment also modified the meal pattern before and during the CMS, showing a decrease of meal number and an increase of meal size with a tendency of reduced total daily food intake. Mild anti-depressive behavioural effects of the Lactobacilli mix were also present. CONCLUSION: Supplementation of mice with LS LS7892 and LG LG6410 decreases sugar consumption suggesting a potential utility of these strains against stress-induced sugar craving.

Neurotensin-Binding Immunoglobulin G in Patients with Parkinson's Disease.

INTRODUCTION: Neurotensin (NTS) is a 13-amino acid neuropeptide functionally linked with the brain dopaminergic system via expression of the NTS peptide or its receptor in dopamine neurons. Neuropeptide-binding immunoglobulins (Igs) are present in humans and can be involved in both physiological and pathological processes. Considering the functional link between NTS and dopamine neurons, we studied the occurrence of NTS-binding IgG autoantibodies in patients with Parkinson's disease (PD). METHODS: Plasma levels of NTS-binding IgG were analyzed using enzyme-linked immunosorbent assay in both male and female PD patents and in age-matched healthy controls. Possible microbial origin of NTS cross-reactive IgG was analyzed by sequence alignment of the 6-amino acid C-terminal NTS pharmacophore with bacterial and viral proteins from the public NCBI database. RESULTS: NTS-binding IgG were detected in the plasma of all study subjects, while their levels were consistently lower in PD patients versus controls (p = 0.0001), independently from age or sex of the study participants. Moreover, PD patients with a more severe stage (2.5-3.0) of the disease had lower levels of NTS-binding IgG (p = 0.0004) than those with a milder stage (1.0-2.0). Furthermore, PD patients taking amantadine or high doses of levodopa had higher levels of NTS-binding IgG than those without medication. Contiguous sequence homology for the NTS pharmacophore was present in several microbial proteins occurring in human gut microbiota. DISCUSSION: The study revealed that NTS-binding IgG occur naturally in humans and that PD patients display their low plasma levels accentuated by disease severity. The functional significance of this finding and its relevance to the pathophysiology of PD, including putative link to gut microbiota, remain to be studied.

Autoantibodies reactive to adrenocorticotropic hormone can alter cortisol secretion in both aggressive and nonaggressive humans.

Violent aggression in humans may involve a modified response to stress, but the underlying mechanisms are not well understood. Here we show that naturally present autoantibodies reactive to adrenocorticotropic hormone (ACTH) exhibit distinct epitope-binding profiles to ACTH peptide in subjects with a history of violent aggression compared with controls. Namely, while nonaggressive male controls displayed a preferential IgG binding to the ACTH central part (amino acids 11-24), subjects who had committed violent acts of aggression had IgG with increased affinity to ACTH, preferentially binding to its N terminus (amino acids 1-13). Purified IgGs from approximately half of the examined sera were able to block ACTH-induced cortisol secretion of human adrenal cells in vitro, irrespective of the source of sample (from a control subject or a violent aggressor). Nevertheless, in the resident-intruder test in mice, i.p. injection of residents with ACTH and IgG from aggressive subjects, but not from control subjects, shortened latency for the first attack against intruders. Immunohistochemical screening of violent aggressors' sera on rat brain and pituitary sections did not show IgG binding to ACTH-producing cells, but 4 of 16 sera revealed selective binding to a nonidentified antigen in vasopressinergic neurons of the hypothalamic paraventricular and supraoptic nuclei. Thus, the data show that ACTH-reactive plasmatic IgGs exhibit differential epitope preference in control and violently aggressive subjects. These IgGs can modulate ACTH-induced cortisol secretion and, hence, are involved in the regulation of the stress response. However, the possible role of ACTH-reactive autoantibodies in aggressive behavior needs further investigation.

Commensal Hafnia alvei strain reduces food intake and fat mass in obese mice-a new potential probiotic for appetite and body weight management.

BACKGROUND/OBJECTIVES: Based on the recent identification of E.coli heat shock protein ClpB as a mimetic of the anorexigenic α-melanocyte stimulating hormone (α-MSH), the objective of this study was to preclinically validate Hafnia alvei, a ClpB-producing commensal bacterium as a potential probiotic for appetite and body weight management in overweight and obesity. METHODS: The involvement of enterobacterial ClpB in the putative anti-obesity effects was studied using ClpB-deficient E.coli. A food-grade H. alvei HA4597 strain synthetizing the ClpB protein with an α-MSH-like motif was selected as a candidate probiotic to be tested in ob/ob and high-fat diet (HFD)-fed obese and overweight mice. The relevance of the enterobacterial ClpB gene to human obesity was studied by in silico analysis of fecal metagenomes of 569 healthy individuals from the "MetaHIT" database. RESULTS: Chronic per os administration of native but not ClpB-deficient E.coli strain reduced body weight gain (p < 0.05) and daily meal frequency (p < 0.001) in ob/ob mice. Oral gavage of H.alvei for 18 and 46 days in ob/ob and HFD-fed obese mice, respectively, was well tolerated, reduced body weight gain and fat mass in both obesity models (p < 0.05) and decreased food intake in hyperphagic ob/ob mice (p < 0.001). Elevated fat tissue levels of phosphorylated hormone-sensitive lipase were detected in H.alvei -treated ob/ob mice (p < 0.01). Enterobacterial ClpB gene richness was lower in obese vs. non-obese humans (p < 0.0001) and correlated negatively with BMI in genera of Enterobacter, Klebsiella and Hafnia. CONCLUSIONS: H.alvei HA4597 strain reduces food intake, body weight and fat mass gain in hyperphagic and obese mice. These data combined with low enterobacterial ClpB gene abundance in the microbiota of obese humans provide the rationale for using H.alvei as a probiotic for appetite and body weight management in overweight and obesity.

Elevated plasma concentrations of bacterial ClpB protein in patients with eating disorders.

OBJECTIVE: Caseinolytic protease B (ClpB) produced by Enterobacteria, such as Escherichia coli, has been identified as a conformational mimetic of α-melanocyte-stimulating hormone (α-MSH), an anorexigenic and anxiogenic neuropeptide. In mice, ClpB induces α-MSH cross-reactive antibodies and activates anorexigenic brain neurons. In patients with eating disorders (ED), anti-ClpB and anti-α-MSH antibodies correlate with psychopathological traits. However, it is not known if ClpB is present in human plasma including ED patients. METHODS: Plasma concentrations of ClpB were measured using a recently developed ClpB immunoassay in female patients with anorexia nervosa, bulimia nervosa, and binge-eating disorder and compared with healthy participants, all characterized by the Eating Disorder Inventory-2 (EDI-2) scale. RESULTS: We found that ClpB was readably detectable in plasma of healthy participants and ED patients and that its concentrations were elevated in ED patients, without significant differences in patient's subgroups. Plasma ClpB concentrations correlated with the EDI-2 scores, with α-MSH as well as with plasma levels of anti-ClpB and anti-α-MSH antibodies. DISCUSSION: These data revealed that bacterial ClpB is naturally present in human plasma and that its concentrations can be elevated in ED patients and associated with ED-related psychopathological traits. These results support a link between bacterial ClpB and the ED pathophysiology. © 2016 Wiley Periodicals, Inc. (Int J Eat Disord 2016; 49:805-808).

Functional role of immunoglobulin G as an oxytocin-carrier protein.

It has been long-time known that oxytocin in plasma is bound to a carrier protein, a common feature of circulating peptide hormones, however, the nature of such protein was uncertain. A recent study revealed that about 60% of oxytocin present in plasma is bound to immunoglobulin G (IgG) and that oxytocin-binding IgG plays a role of a functional oxytocin carrier protein. Here, we review the historical background and methodology leading to this discovery. Moreover, we review the data showing the functional role of oxytocin-binding IgG in the modulation of oxytocin signaling relevant to the regulation of motivated behavior and several neuropsychiatric disorders. Furthermore, the possible role of gut microbiota in the origin of such IgG is discussed and the relevant new therapeutic strategies for the enhancement of oxytocin signaling are presented.

Gut Microbiota-Brain Axis in Regulation of Feeding Behavior.

The survival of microorganisms inhabiting the intestinal tract depends on the nutrients provided by the host, with the latter obtaining them through food intake. It is hence not surprising that the co-evolution of gut bacteria and their hosts, including humans, shaped intrinsic interactions between their respective metabolisms with an impact on host feeding behavior. Understanding molecular pathways underlying such interactions may aid in the development of new therapeutic approaches for several pathological conditions accompanied by altered feeding behavior. A Special Issue titled "Gut Microbiota-Brain Axis in Regulation of Feeding Behavior" contributes to this topic of research, with eight papers covering its various aspects such as autoprobiotics, metabolic diseases and anorexia.

Blood Levels of Neuropeptide 26RFa in Relation to Anxiety and Aggressive Behavior in Humans-An Exploratory Study.

26RFa, also referred to as QRFP, is a hypothalamic neuropeptide mainly known for its role in the regulation of appetite and glucose metabolism. Its possible relevance to emotional regulation is largely unexplored. To address this, in the present exploratory study, we analyzed the plasma concentrations of 26RFa in humans characterized by different levels of anxiety and aggressive behavior. For this purpose, the study included 13 prison inmates who have committed violent crimes and 19 age-matched healthy men from the general population as controls. Anxiety, depression and aggressive behavior were evaluated in both groups using standard questionnaires. The inmate group was characterized by increased aggression and anxiety compared to the controls. We found that the mean plasma levels of 26RFa did not significantly differ between the inmates and the controls. However, several high outliers were present only in the inmate group. The plasma levels of 26RFa correlated positively with the anxiety scores in all the studied subjects and controls. After removing the high outliers in the inmate group, positive correlations of 26RFa with anxiety and a subscale of hostility in the aggression scale were also recorded in this group. No significant correlations of 26RFa with depression scores or other parameters of aggressive behavior were found. Thus, the present results did not support an involvement of 26RFa in aggressive behavior in humans but pointed to a link between this neuropeptide and anxiety. Nevertheless, considering the exploratory nature of the present study, this conclusion should be verified in a larger cohort, including the clinical degree of anxiety.

Immunoglobulin G is a natural oxytocin carrier which modulates oxytocin receptor signaling: relevance to aggressive behavior in humans.

Oxytocin is a neuropeptide produced mainly in the hypothalamus and secreted in the CNS and blood. In the brain, it plays a major role in promoting social interactions. Here we show that in human plasma about 60% of oxytocin is naturally bound to IgG which modulates oxytocin receptor signaling. Further, we found that IgG of violent aggressive inmates were characterized by lower affinity for oxytocin, causing decreased oxytocin carrier capacity and reduced receptor activation as compared to men from the general population. Moreover, peripheral administration of oxytocin together with human oxytocin-reactive IgG to resident mice in a resident-intruder test, reduced c-fos activation in several brain regions involved in the regulation of aggressive/defensive behavior correlating with the attack number and duration. We conclude that IgG is a natural oxytocin carrier protein modulating oxytocin receptor signaling which can be relevant to the biological mechanisms of aggressive behavior.

Gastric electrical stimulation increases ghrelin production and inhibits catecholaminergic brainstem neurons in rats.

Gastric electrical stimulation (GES) is a new therapeutic option for functional dyspepsia and gastroparesis. In addition to ameliorating nausea and vomiting, GES results in improved appetite which is not always associated with accelerated gastric emptying. To explore the central and peripheral factors underlying GES-associated improvement of appetite we developed a GES model in anaesthetized Wistar rats. During laparotomy, two electrodes were implanted into the stomach and high-frequency low-energy GES (14 Hz, 5 mA) was applied. The effects of 1 h GES were compared with sham stimulation. After GES, c-Fos expression was increased in the mucosal and submucosal layers of the stimulated area (174%). In the stomach, GES increased ghrelin mRNA (178%) and doubled the number of ghrelin-positive cells, resulting in elevated plasma levels of ghrelin (2.3 ± 0.2 vs. 1.6 ± 0.2 ng/mL). In the arcuate nucleus of the hypothalamus, GES increased c-Fos (277%) and agouti-related protein (AgRP) mRNA expression (135%). GES reduced the number of c-Fos-positive cells throughout the nucleus of the solitary tract (between 93 and 75% from rostral to caudal levels) including catecholaminergic neurons (81% at caudal level). Gastric emptying, plasma glucose and heart rate variability were not affected by GES. This study shows that GES may improve appetite via stimulation of main orexigenic pathways, including ghrelin production in the stomach and AgRP in the hypothalamus, as well as by reducing the activity of catecholaminergic brainstem neurons.

The new link between gut-brain axis and neuropsychiatric disorders.

PURPOSE OF REVIEW: Although the cause of most neuropsychiatric disorders remains uncertain, new data offer alternative explanations warranting further validations. This review summarizes some recent findings that may localize the origin of eating disorders as well as some other neuropsychiatric disorders outside the brain and discuss their cause as a possible dysfunction of the gut-brain axis involving the humoral immune system. RECENT FINDINGS: The gut microbiota has been identified as the main source of highest biological variability confined in an individual and also provides constant antigenic stimulation shaping up the physiological immune response. Furthermore, molecular mimicry has been shown among microbial proteins including gut microbiota and several key neuropeptides involved in the regulation of motivated behavior and emotion. Immunoglobulins reactive with these neuropeptides have been identified in humans, and their levels or affinities were associated with neuropsychiatric conditions including anxiety, depression, eating and sleep disorders. SUMMARY: Cross-reacting immunoglobulins may bind both microbial sequences and neuropeptides, thereby constituting a particular way of signaling between the gut and the brain. Alteration of this link may contribute to several neuropsychiatric disorders, emphasizing the key role of nutrition among other factors influencing gut content and intestinal permeability.

Mechanisms of Glucose Absorption in the Small Intestine in Health and Metabolic Diseases and Their Role in Appetite Regulation.

The worldwide prevalence of metabolic diseases such as obesity, metabolic syndrome and type 2 diabetes shows an upward trend in recent decades. A characteristic feature of these diseases is hyperglycemia which can be associated with hyperphagia. Absorption of glucose in the small intestine physiologically contributes to the regulation of blood glucose levels, and hence, appears as a putative target for treatment of hyperglycemia. In fact, recent progress in understanding the molecular and cellular mechanisms of glucose absorption in the gut and its reabsorption in the kidney helped to develop a new strategy of diabetes treatment. Changes in blood glucose levels are also involved in regulation of appetite, suggesting that glucose absorption may be relevant to hyperphagia in metabolic diseases. In this review we discuss the mechanisms of glucose absorption in the small intestine in physiological conditions and their alterations in metabolic diseases as well as their relevance to the regulation of appetite. The key role of SGLT1 transporter in intestinal glucose absorption in both physiological conditions and in diabetes was clearly established. We conclude that although inhibition of small intestinal glucose absorption represents a valuable target for the treatment of hyperglycemia, it is not always suitable for the treatment of hyperphagia. In fact, independent regulation of glucose absorption and appetite requires a more complex approach for the treatment of metabolic diseases.

The Probiotic Strain H. alvei HA4597® Improves Weight Loss in Overweight Subjects under Moderate Hypocaloric Diet: A Proof-of-Concept, Multicenter Randomized, Double-Blind Placebo-Controlled Study.

Background: Increasing evidence supports the role of the gut microbiota in the control of body weight and feeding behavior. Moreover, recent studies have reported that the probiotic strain Hafnia alvei HA4597® (HA), which produces the satietogenic peptide ClpB mimicking the effect of alpha-MSH, reduced weight gain and adiposity in rodent models of obesity. Methods: To investigate the clinical efficacy of HA, 236 overweight subjects were included, after written informed consent, in a 12-week prospective, double-blind, randomized study. All subjects received standardized counselling for a -20% hypocaloric diet and were asked to maintain their usual physical activity. Subjects of the HA group received two capsules per day providing 100 billion bacteria per day and subjects in the Placebo (P) group received two placebo capsules. The primary endpoint was the percentage of subjects achieving a weight loss of at least 3% after 12 weeks. Intention-to-treat statistical analysis was performed using exact-Fischer, Mann-Whitney and paired-Wilcoxon tests as appropriate. Results: In the HA group, significantly more subjects (+33%) met the primary endpoint than in the P group (54.9 vs. 41.4%, p = 0.048). In the HA group, an increased feeling of fullness (p = 0.009) and a greater loss of hip circumference (p < 0.001) at 12 weeks were also observed. Fasting glycemia at 12 weeks was significantly lower (p < 0.05) in the HA compared to P group. Clinical and biological tolerance was good in both groups. Conclusions: A 12-week treatment with the probiotic strain H. alvei HA4597® significantly improves weight loss, feeling of fullness and reduction of hip circumference in overweight subjects following moderate hypocaloric diet. These data support the use of H. alvei HA4597® in the global management of excess weight.

Psychopathological and personality features in primary Sjogren's syndrome--associations with autoantibodies to neuropeptides.

OBJECTIVES: To determine the spectrum of personality and psychopathology features of patients with primary SS (pSS) and explore whether they are linked to disease characteristics as well as the presence of autoantibodies (autoAbs) against neuropeptides. METHODS: Personality and psychopathological variables were determined in 103 pSS patients and 110 healthy controls (HCs). AutoAbs against hypothalamic and pituitary neuropeptides were measured by ELISA in 25 pSS patients and 25 HCs. Data analysis was performed by univariate and multivariate logistic regression models and by comparison with regression models. RESULTS: A higher number of pSS patients reported distinct personality traits (neuroticism, psychoticism and obsessiveness) and psychological distress compared with HCs. After adjustment for personality characteristics and demographics, only hypochondriasis was the main psychopathology feature associated with pSS, suggesting that psychopathological manifestations in the setting of pSS are primarily dependent on premorbid personality characteristics. Although no differences were detected between serum levels of neuropeptide autoAbs in pSS cases and controls, levels of autoAbs against alpha-melanocyte-stimulating hormone (alpha-MSH) correlated with anxiety scores in both groups examined but with higher intercept in pSS subjects. Significant correlations between anxiety score and autoAbs directed against oxytocin and vasopressin were also detected in the pSS patients. CONCLUSIONS: pSS patients exhibit a distinct pattern of personality traits and high levels of psychological distress compared with HCs, which seems to be determined by premorbid personality characteristics. Correlations between anxiety and alpha-MSH autoAbs suggest their potential involvement in anxiety development in both pSS and HCs.

Serotonin delivery into the ventromedial nucleus of the hypothalamus affects differently feeding pattern and body weight in obese and lean Zucker rats.

AIM: To determine if central serotonin (5-HT)-induced satiety is altered in obesity. METHODS: Obese and lean Zucker rats received infusion of 5-HT (5 microg/0.5 microl/h) or saline into the ventromedial nucleus of the hypothalamus (VMN) for 2 weeks. RESULTS: In lean rats, 5-HT decreased body weight (7%) and total food intake (15%) which was due to a decreased meal size during the dark phase. In obese rats, a decrease of food intake was also observed in the dark phase, but it was compensated by an increased food intake during the light phase, resulting in no significant changes of total food intake and body weight. In obese rats, meal number but not meal size was affected by 5-HT delivery. Body fat content was not affected by 5-HT in obese rats, while cessation of 5-HT delivery in lean rats resulted in 13% increase. CONCLUSION: Intra-VMN 5-HT in obese rats did not increase meal-associated satiety as it did in lean rats, but modulated hunger. These results show that the Zucker obese phenotype is characterized by VMN resistance to 5-HT, which may contribute to neurobiological mechanisms of increased meal size and food intake and may diminish anti-obesity effects of serotonergic anorexiants.

Food intake and meal pattern in response to hyperosmotic-induced dehydration in obese and lean Zucker rats.

OBJECTIVES: Obese Zucker rats display neurochemical modifications in the brain characteristic of dehydration, but are nevertheless hyperphagic. This suggests that the obese animals can be resistant to dehydration-induced anorexia. The aim of this study was to test the hypothesis by comparing the effects of dehydration on food intake and feeding pattern between obese and lean Zucker rats. METHODS: Intracellular dehydration in obese (fa/fa) and lean (Fa/Fa) Zucker rats was induced by replacing drinking water with hyperosmotic sodium chloride solutions (1.8% and 2.7%, consecutively, 4 d each). Daily food intake, meal size, and meal number were measured using an automated computerized rat eater meter before, during, and after the dehydration. RESULTS: After 8 d of hyperosmotic challenge, body weight decreased by 15% and 10% in lean and obese rats, respectively. Obese rats displayed higher food intake and meal size than lean rats before, during, and after the dehydration. Drinking 1.8% and 2.7% sodium chloride solutes decreased gradually food intake and meal size in both lean and obese rats; however, obese rats had a higher percentage of food intake than lean rats during the osmotic challenge. Higher ratios of food to water intake characterized obese rats and the percentage of such ratios in obese versus lean rats were increased during the 2.7% sodium chloride load. Meal number was not affected by dehydration in obese rats, but it was decreased in lean rats during the 2.7% sodium chloride load and remained low during refeeding after the dehydration, when the meal size was increased. CONCLUSION: Dehydration-induced anorexia is present in both obese and lean Zucker rats; however, obese rats are more resistant to dehydration by preserving their meal size and food intake. These results support a role for feeding-associated dehydration in the pathogenesis of hyperphagia and obesity.

Plasma enterobacterial ClpB levels and ClpB- and α-MSH-reactive immunoglobulins in lung cancer patients with and without anorexia.

OBJECTIVES: Anorexia represents a common and debilitating clinical problem in patients with several forms of cancer, in particular lung cancer, but its mechanisms are not completely understood. Recently, the caseinolytic-protease-B (ClpB) homologue protein, produced by common gut bacteria, such as Escherichia coli, was identified as an antigen-mimetic of α-melanocyte-stimulating hormone (α-MSH), an anorexigenic neuropeptide. ClpB was previously detected in human plasma and displayed satietogenic properties; however, its possible relevance to cancer anorexia has not yet been investigated. METHODS: To address this question, we analyzed plasma ClpB concentrations as well as levels and affinities of anti-ClpB and α-MSH-reactive antibodies in patients with lung cancer with and without anorexia as compared with body mass index-matched healthy controls with normal appetite. RESULTS: We found that plasma ClpB concentrations were significantly lower in non-anorexic patients with cancer than those of the control group (P = 0.028). In contrast, patients with cancer and anorexia had lower levels of anti-ClpB immunoglobulins (Ig)M (P < 0.0001) and of both α-MSH IgM and IgG (P < 0.05) with respect to controls. Moreover, in patients with cancer and anorexia, anti-ClpB IgG showed a trend of lower affinities compared with non-anorexic patients (P = 0.05). CONCLUSIONS: Taken together, the results revealed a reduced humoral immune response to ClpB in patients with cancer and anorexia, which may lead to an enhanced satietogenic effect of this enterobacterial protein contributing to the mechanisms of reduced appetite.

Host Starvation and Female Sex Influence Enterobacterial ClpB Production: A Possible Link to the Etiology of Eating Disorders.

Altered signaling between gut bacteria and their host has recently been implicated in the pathophysiology of eating disorders, whereas the enterobacterial caseinolytic protease B (ClpB) may play a key role as an antigen mimetic of α-melanocyte-stimulating hormone, an anorexigenic neuropeptide. Here, we studied whether ClpB production by gut bacteria can be modified by chronic food restriction and female sex, two major risk factors for the development of eating disorders. We found that food restriction increased ClpB DNA in feces and ClpB protein in plasma in both male and female rats, whereas females displayed elevated basal ClpB protein levels in the lower gut and plasma as well as increased ClpB-reactive immunoglobulins (Ig)M and IgG. In contrast, direct application of estradiol in E. coli cultures decreased ClpB concentrations in bacteria, while testosterone had no effect. Thus, these data support a mechanistic link between host-dependent risk factors of eating disorders and the enterobacterial ClpB protein production.