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PubMed2007

Adiponectin and resistin in human cerebrospinal fluid and expression of adiponectin receptors in the human hypothalamus.

CONTEXT: The adipokine leptin has critical importance in central appetite regulation. In contrast to some suggestion of adiponectin influencing energy homeostasis in rodents, there is no evidence for adiponectin or resistin entering the human blood-brain barrier. OBJECTIVE: The objective was to establish the presence of adiponectin or resistin in human cerebrospinal fluid (CSF) and to compare their distribution with leptin. Furthermore, we wished to examine the expression of the adiponectin receptors 1 and 2 (AdipR1, AdipR2) in the human hypothalamus. METHODS: For this purpose, serum and CSF samples were collected from 20 men and 19 women matched for age [men, 69.8 +/- 8.6 yr (mean +/- SD); women, 69.4 +/- 4.3 yr] and BMI (men, 29.4 +/- 3.4 kg/m(2); women, 27.3 +/- 4.8 kg/m(2)) undergoing elective surgery under spinal anesthesia. RESULTS: Adiponectin was identified in CSF with levels 1000-fold less than serum, whereas resistin and leptin levels were 100-fold less. Unlike their serum levels, adiponectin CSF levels showed no gender difference or correlation with insulin resistance, which is similar to resistin CSF levels. The adiponectin and leptin CSF/serum ratios in our study exhibit the same pattern of gender-specific BMI association with inverse correlation in women (r = -0.61; P = 0.02) and no correlation in men (r = 0.026; P = not significant). Furthermore, immunostaining established AdipR1 and -2 in the hypothalamus and increased AdipR2 expression in the paraventricular nucleus, which is involved in energy regulation. CONCLUSION: In summary, our findings show both the presence of adiponectin and resistin in human CSF, with no effect of insulin resistance on CSF levels. The CSF entry of adiponectin and leptin in women appears to be impaired in obesity.

Adiponectin↗
PubMed1997

Interleukin 1 alpha increases serum leptin concentrations in humans.

Leptin, the protein product of the ob gene, regulates appetite and body weight in animals. Endotoxin and cytokines, induced by endotoxin, interleukin (IL) 1 and tumor necrosis factor, increase expression of leptin in mice and hamsters. We measured serum leptin concentrations in patients with cancer before and after administration of recombinant human IL-1 alpha. Fourteen patients received IL-1 alpha at one of three dose levels (0.03, 0.1, or 0.3 microgram/kg.day) for 5 days. Serum leptin concentrations increased in all but two patients within 24 h after the first dose. The increase in leptin was correlated directly with IL-1 alpha dose (P = 0.0030). Despite continued administration of IL-1 alpha, serum leptin concentrations returned to pretreatment levels by day 5 of therapy. An increase in serum leptin concentrations may be one mechanism by which anorexia is induced by IL-1 alpha. However, tachyphylaxis of the leptin response suggests that other mechanisms also are involved.

Adult↗
PubMed1998

Disruption of the relationship between fat content and leptin levels with aging in humans.

Leptin released from adipose tissue is believed to participate in a negative feedback loop regulating appetite, and malfunction of this mechanism could lead to obesity. We measured plasma leptin and body composition (dual energy x-ray absorptiometry) in 70 healthy subjects, divided into 3 age groups (young, 25 +/- 1 yr; middle-aged, 53 +/- 1 yr; old, 70 +/- 1 yr), while on a 5-day weight-maintaining diet. Pairwise correlations were assessed using product-moment correlation, and regression analysis was used to evaluate relationships between leptin and other variables. Leptin concentrations and relative body fat content were correlated in young females (r = 0.71; P = 0.009) and in young males (r = 0.76; P = 0.007), but not in the combined middle-aged and elderly groups (r = 0.19; P = 0.36 and r = 0.19; P = 0.38 in females and males, respectively). Regression analysis showed a clear correlation between circulating leptin and relative fat mass in the young subjects (P = 0.0001), but not in the older subjects (P = 0.199). We conclude that body fat content in young subjects correlates with plasma leptin in both genders, whereas this relationship is disrupted in elderly subjects, thus possibly contributing to the obesity occurring with age.

Absorptiometry, Photon↗
PubMed2006

Fat aussie--a new Alström syndrome mouse showing a critical role for ALMS1 in obesity, diabetes, and spermatogenesis.

Mutations in the human ALMS1 gene are responsible for Alström syndrome, a disorder in which key metabolic and endocrinological features include childhood-onset obesity, metabolic syndrome, and diabetes, as well as infertility. ALMS1 localizes to the basal bodies of cilia and plays a role in intracellular trafficking, but the biological functions of ALMS1 and how these relate to the pathogenesis of obesity, diabetes, and infertility remain unclear. Here we describe a new mouse model of Alström syndrome, fat aussie, caused by a spontaneous mutation in the Alms1 gene. Fat aussie (Alms1 foz/foz) mice are of normal weight when young but, by 120 d of age, they become obese and hyperinsulinemic. Diabetes develops in Alms1 foz/foz mice accompanied by pancreatic islet hyperplasia and islet cysts. Female mice are fertile before the onset of obesity and metabolic syndrome; however, male fat aussie mice are sterile due to a progressive germ cell loss followed by an almost complete block of development at the round-to-elongating spermatid stage of spermatogenesis. In conclusion, Alms1 foz/foz mouse is a new animal model in which to study the pathogenesis of the metabolic and fertility defects of Alström syndrome, including the role of ALMS1 in appetite regulation, pathogenesis of the metabolic syndrome, pancreatic islet physiology, and spermatogenesis.

Animals↗
PubMed2005

Medications associated with weight gain.

OBJECTIVE: To review available literature regarding weight gain associated with commonly prescribed drugs and adjunctive therapy used to limit weight gain. DATA SOURCES: Information was retrieved from a MEDLINE English-literature search between 1995 and July 2005, with a major subject heading of weight gain/drug effects excluding complementary alternative medicines. Other limits applied included human subjects and individuals >19 years of age. Additionally, references from retrieved articles were reviewed to identify other literature sources. STUDY SELECTION AND DATA EXTRACTION: Changes in weight are generally reported as a primary or secondary outcome of many studies. Where possible, prospective, randomized, controlled trials were preferred; however, many studies were retrospective or open label. Meta-analyses and recent reviews, especially those providing a detailed description of the proposed mechanism involved in weight gain beyond the scope of this article, were included. Limited information was available from case reports. Studies were categorized by therapeutic area including psychiatry, neurology, diabetes, and other miscellaneous drug therapy. Medications used to intentionally stimulate appetite for weight gain, such as megesterol acetate, were not included. DATA SYNTHESIS: Weight gain with medication is usually associated with individual agents within a class. The tendency to cause weight gain is often related to differential specificity and sensitivity of binding to receptors involved with appetite regulation. CONCLUSIONS: Clinically significant weight gain is associated with some commonly prescribed medicines. There is wide interindividual variation in response and variation of the degree of weight gain within drug classes. Where possible, alternative therapy should be selected, especially for individuals predisposed to overweight and obesity.

Antidepressive Agents↗
PubMed2001

Pharmacodynamics of drug-induced weight gain.

Body weight gain during treatment with drugs for any kind of disease may represent improvement of the disease itself. However, sometimes these drug-induced alterations of the body's appetite-regulating mechanisms result in excessive weight gain, thus jeopardizing compliance with prescribed medication. A number of drugs are capable of changing body weight as an adverse consequence of their therapeutic effect. Included in this category are the psychotropic drugs such as antipsychotics, antidepressants and mood stabilizers. Antipsychotics are well-known culprits of weight gain. The low-potency (e.g., chlorpromazine and thioridazine) and atypical agents (e.g., clozapine, olanzapine, quetiapine and risperidone) are most often associated with weight gain. Antidepressants such as tricyclic antidepressants and monoamine oxidase (MAO) inhibitors are most often associated with significant weight gain. The tertiary tricyclic antidepressant amitriptyline is thought to induce the most weight gain. Mood stabilizers such as lithium carbonate, valproic acid and carbamazepine also induce weight gain in a considerable number of patients. Treatment with corticosteroids is associated with dose-dependent body weight gain in many patients and corticosteroid-induced obesity aggravates other corticosteroid-associated health risks. Insulin therapy in diabetic patients usually increases body weight. Finally, sulfonylurea derivatives, antineoplastic agents used for the treatment of breast cancer and several drugs used in migraine prophylaxis may cause body weight gain as well. (c) 2001 Prous Science. All rights reserved.

Journal Article↗
PubMed2002

Leptin inhibits osteoclast generation.

Originally, leptin was described as a product of adipocytes that acts on the hypothalamus to regulate appetite. However, subsequently, it has been shown that leptin receptors are distributed widely and that leptin has diverse functions, including promotion of hemopoietic and osteoblastic differentiation. It has been recognized for some time that both serum leptin and bone mass are correlated positively to body fat mass and, recently, we have shown a direct positive relationship between serum leptin and bone mass in nonobese women. We now report that leptin inhibits osteoclast generation in cultures of human peripheral blood mononuclear cells (PBMCs) and murine spleen cells incubated on bone in the presence of human macrophage colony-stimulating factor (hM-CSF) and human soluble receptor activator of NF-kappaB ligand (sRANKL). The half-maximal concentration inhibitory of leptin was approximately 20 nM in the presence of sRANKL at 40 ng/ml but decreased to approximately 2 nM when sRANKL was used at 5 ng/ml. The majority of the inhibitory effect occurred in the first week of the 3-week cultures. Inhibition did not occur when the PBMC cultures were washed vigorously to remove nonadherent cells or when purified CD14+ monocytes were used to generate osteoclasts, indicating an indirect or permissive effect via CD14- PBMC. Leptin increased osteoprotegerin (OPG) messenger RNA (mRNA) and protein expression in PBMC but not in CD14+ cells, suggesting that the inhibitory effect may be mediated by the RANKL/RANK/OPG system. Leptin may act locally to increase bone mass and may contribute to linkage of bone formation and resorption.

Animals↗
PubMed2004

Translational medicine in fish-derived peptides: from fish endocrinology to human physiology and diseases.

Recent studies have revealed the importance of fish-derived peptide hormones to human endocrinology. These peptides include melanin-concentrating hormone (MCH), urocortins (human urotensin-I), and urotensin-II. MCH, a hypothalamic peptide, is a potent stimulator on appetite. Urocortins, e.g. urocortin 1 and urocortin 3 (stresscopin), are endogenous ligands for the corticotropin-releasing factor (CRF) receptors, particularly CRF type 2 receptor, that mediates a vasodilator action, a positive inotropic action and a central appetite-inhibiting action. These actions mediated by CRF type 2 receptor may ameliorate the stress response. Human urotensin-II is a potent vasoconstrictor peptide, while it acts as a vasodilator on some arteries. Human urotensin-II is expressed in various types of cells and tissues, including cardiovascular tissues, as well as many types of tumor cells. Thus, these fish-derived peptides appear to play important roles in human physiology, such as appetite regulation, stress response and cardiovascular regulation, and also in diseases, for example, obesity, cardiovascular diseases and tumors. Development of antagonists/agonists against the receptors for these peptides may open new strategies for the treatment of various diseases, including obesity-related diseases, hypertension, heart failure and malignant tumors.

Animals↗
PubMed2004

Analysis of candidate genes in Polish families with obesity.

This study analyzes the relationship between risk factors related to overweight/obesity, insulin resistance, lipid tolerance, hypertension, endothelial function and genetic polymorphisms associated with: i) appetite regulation (leptin, melanocortin-3-receptor (MCR-3), dopamine receptor 2 (D2R)); ii) adipocyte differentiation and insulin sensitivity (peroxisome proliferator-activated receptor-gamma2 (PPAR-gamma2), tumor necrosis factor-alpha (TNF-alpha)); iii) thermogenesis and free fatty acid (FFA) transport/catabolism (uncoupling protein-1 (UCP1), lipoprotein lipase (LPL), beta2- and beta3-adrenergic receptor (beta2AR, beta3AR), fatty acid transport protein-1 (FATP-1) and iv) lipoproteins (apoliprotein E (apoE), apo CIII). The 122 members of 40 obese Caucasian families from southern Poland participated in the study. The genotypes were analyzed by restriction fragment length polymorphism-polymerase chain reaction (RFLP-PCR) or by direct sequencing. Phenotypes related to obesity (body mass index (BMI), fat/lean body mass composition, waist-to-hip ratio (WHR)), fasting lipids, glucose, leptin and insulin, as well as insulin during oral glucose tolerance test (OGTT) (4 points within 2 hours) and during oral lipid tolerance test (OLTT) (5 points within 8 hours) were assessed. The insulin sensitivity indexes: homeostasis model assessment of insulin resistance, whole body insulin sensitivity index, hepatic insulin sensitivity and early secretory response to an oral glucose load (HOMA-IR, ISI-COMP, ISI-HOMA and DELTA) were calculated. The single gene mutations such as C105 T OB and Pro115 Gln PPAR-gamma2 linked to morbid obesity were not detected in our group. A weak correlation between obesity and certain gene polymorphisms was observed. Being overweight (25 < BMI > or = 30 kg/m2) significantly correlated with worse FFA tolerance in male PPAR-gamma2 12Pro, LPL-H (G) allele carriers. Insulin resistance was found in female PPAR-gamma2 Pro12, TNF-alpha (-308A) and LPL-H (G) allele carriers. Hypertension linked to the PPAR-gamma2 Pro allele carriers was characterized by high leptin output during OLTT. We conclude that the polymorphisms we investigated were weakly correlated with obesity but significantly modified the risk factors of the metabolic syndrome.

Adult↗
PubMed2006

Terminal nerve-derived neuropeptide y modulates physiological responses in the olfactory epithelium of hungry axolotls (Ambystoma mexicanum).

The vertebrate brain actively regulates incoming sensory information, effectively filtering input and focusing attention toward environmental stimuli that are most relevant to the animal's behavioral context or physiological state. Such centrifugal modulation has been shown to play an important role in processing in the retina and cochlea, but has received relatively little attention in olfaction. The terminal nerve, a cranial nerve that extends underneath the lamina propria surrounding the olfactory epithelium, displays anatomical and neurochemical characteristics that suggest that it modulates activity in the olfactory epithelium. Using immunocytochemical techniques, we demonstrate that neuropeptide Y (NPY) is abundantly present in the terminal nerve in the axolotl (Ambystoma mexicanum), an aquatic salamander. Because NPY plays an important role in regulating appetite and hunger in many vertebrates, we investigated the possibility that NPY modulates activity in the olfactory epithelium in relation to the animal's hunger level. We therefore characterized the full-length NPY gene from axolotls to enable synthesis of authentic axolotl NPY for use in electrophysiological experiments. We find that axolotl NPY modulates olfactory epithelial responses evoked by l-glutamic acid, a food-related odorant, but only in hungry animals. Similarly, whole-cell patch-clamp recordings demonstrate that bath application of axolotl NPY enhances the magnitude of a tetrodotoxin-sensitive inward current, but only in hungry animals. These results suggest that expression or activity of NPY receptors in the olfactory epithelium may change with hunger level, and that terminal nerve-derived peptides modulate activity in the olfactory epithelium in response to an animal's changing behavioral and physiological circumstances.

Ambystoma↗
PubMed1997

Lack of effects of circulating thyroid hormone levels on serum leptin concentrations.

Leptin is the protein product of the ob gene, secreted by adipocytes. It has been suggested that it may play an important role in regulating appetite and energy expenditure. The aim of this study was to evaluate a possible interaction of thyroid hormones with the leptin system. We studied 114 adult patients (65 females and 49 males): 36 were affected with primary hypothyroidism (PH), 38 with central hypothyroidism (CH) and 40 with thyrotoxicosis (TT). Patients with CH were studied both before and after 6 months of L-thyroxine replacement therapy. Body mass index (BMI; kg/m2), thyroid function and fasting serum leptin were assessed in all patients. Since BMI has been proved to be the major influencing variable of circulating leptin levels, data were expressed as standard deviation score (SDS) calculated from 393 male and 561 female controls matched for age and BMI. No difference in SDS was recorded between males and females whatever the levels of circulating thyroid hormones. In males, no significant difference was recorded among the SDSs of PH (-0.36 +/- 1.2), TT (-0.35 +/- 1.2) and CH (0.01 +/- 1.4) patients. Females with PH had an SDSs significantly lower than TT females (-0.77 +/- 1.0 vs -0.06 +/- 1.2; P < 0.02), while no significant differences between CH (-0.34 +/- 0.7) and TT females or between CH and PH females were observed. SDS in CH patients after 6 months of L-thyroxine therapy significantly varied only in females (0.25 +/- 1.4). In conclusion, circulating thyroid hormones do not appear to play any relevant role in leptin synthesis and secretion. However, as females with either overt hypo- or hyper-thyroidism or central hypothyroidism after L-thyroxine therapy show differences in their SDSs, a subtle interaction between sex steroids and thyroid status in modulating leptin secretion, at least in women, may occur.

Adult↗
PubMed2006

Ghrelin, insulin sensitivity and postprandial glucose disposal in overweight and obese children.

OBJECTIVE: To explore the changes of ghrelin circulating levels induced by a mixed meal and their relationship with postprandial substrate oxidation rates in overweight and obese children with different levels of insulin sensitivity. METHODS: A group of ten boys (age 9-12 years) with different levels of overweight (standard deviation score of body mass index: 1.6-3.2) was recruited. Body composition was measured by dual-energy X-ray absorptiometry. Insulin sensitivity was assessed by a frequently sampled i.v. glucose tolerance test. Pre-prandial and postprandial (3 h) substrate oxidation was measured by indirect calorimetry. The energy content of the test meal (16% protein, 36% carbohydrate and 48% fat) was 40% of pre-prandial energy expenditure (kJ/day). RESULTS: Pre-prandial serum concentration of total ghrelin was 701.4+/-66.9 pg/ml (S.E.M.). The test meal induced a rapid decrease in ghrelin levels and maximal decrease was 27.3+/-2.7% below baseline. Meal intake induced a progressive increase of the carbohydrate oxidation rate for 45 min after food ingestion, followed by a slow decrease without returning to pre-prandial values. Postprandial cumulative carbohydrate oxidation was 16.9+/-0.8 g/3 h. Insulin sensitivity and postprandial maximal decrease of ghrelin concentration showed a significant correlation (r = 0.803, P < 0.01). Moreover, the postprandial carbohydrate oxidation rate correlated with the area under the curve for both insulin (r = 0.673, P < 0.03) and ghrelin (r = -0.661, P < 0.04). CONCLUSIONS: A relevant association between postprandial insulin-mediated glucose metabolism and ghrelin secretion in children with different levels of overweight was found. It is possible that the maintenance of an adequate level of insulin sensitivity and glucose oxidation may affect appetite regulation by favoring a more efficient postprandial ghrelin reduction.

Blood Glucose↗
PubMed2002

Circulating ghrelin concentrations are lowered by intravenous glucose or hyperinsulinemic euglycemic conditions in rodents.

Ghrelin is a peptide secreted mainly by gastric parietal cells that may play a role in appetite regulation. Circulating ghrelin is abruptly lowered by food intake, but factors involved in ghrelin regulation remain unclear. The aim of this study was to determine whether intravenous glucose infusion lowers ghrelin, and to determine whether glucose, insulin or some measure of insulin action best predicts the effect of feeding on ghrelin. Rats were infused over 3 h with either A. saline (controls); B. dextrose to steady state blood glucose approximately 16.7 mM, or C. insulin 7.5 mU/kg x min, plus dextrose as needed to clamp to euglycemic basal concentrations. During 3 h of infusion, group B had significantly greater (P<0.01) glucose, 17.4+/-0.3 mM, than groups A (6.6+/-0.3) or C (6.1+/- 0.2). Groups B and C had hyperinsulinemia at the end of the 3 h infusion (894+/-246, 804+/-156 pM) compared with saline-infused (222+/-24 pM, P<0.01). Ghrelin concentrations were reduced (P<0.01) in both hyperinsulinemic groups (B=85+/-2; C=103+/-0.6 pM) versus controls (163+/-9). Ghrelin was strongly correlated with insulin (r=-0.68), glucose infusion rate (r=-0.75) and free fatty acids (r=0.67), when all 3 groups were combined, although only the 2 latter variables were independent predictors of ghrelin. In conclusion, neither a rise in blood glucose nor presence of nutrient in the stomach is required for the effect of feeding on ghrelin. The data suggest that whole body insulin responsiveness plays either a direct or indirect role in meal-related ghrelin inhibition.

Animal Feed↗
PubMed2006

Selective agents for serotonin2C (5-HT2C) receptor.

The serotonin2C (5-HT2C) receptor has attracted a lot of attention owing to its role in appetite regulation, depression, obsessive-compulsive disorder (OCD), panic disorders, and substance abuse. This review summarizes non-patent and patent literature up to November 2005 that deals with the synthesis and characterization of selective 5-HT2C receptor agonists and antagonists. Highlights on structure-activity relationships have been included, when possible.

Animals↗
PubMed2006

POMC and orexin mRNA expressions induced by anticipation of a corn-oil emulsion feeding are maintained at the high levels until oil ingestion.

We investigated the gene expression dynamics of several hypothalamic neuropeptides associated with appetite regulation when rats are anticipating being fed a corn-oil emulsion. For 5 days at the same hour each day, rats were fed 5% corn oil emulsified with 0.3% xanthan gum or the vehicle for 20 min. On Day 6, the 5% corn oil emulsion or the vehicle (Vehicle) was presented to the rats, some of which (Oil-intake) were allowed to eat it and some of which (Oil-anticipation) were kept from eating it. Despite waiting a corn-oil, the mRNA levels of proopiomelanocortin (POMC), a beta-endorphin precursor, and orexin showed increases, and high levels of mRNAs of POMC and orexin were maintained for 30 min after the corn-oil was placed before the rats, and only gradually decreased through 150 min. However, the mRNA levels of POMC and orexin in the hypothalamus were decreased within 30 min after starting to ingest the corn-oil emulsion. These results suggest that POMC and orexin mRNA expression was induced by the anticipation in rats after learning the palatability of 5% corn oil emulsion, and the induced mRNA expression based on the anticipation was maintained for at least for 30 min as the rats eagerly waited for ingestion.

Animal Feed↗
PubMed1989

Increased neuropeptide Y concentrations in specific hypothalamic regions of streptozocin-induced diabetic rats.

Untreated streptozocin-induced diabetic (STZ-D) rats have previously been shown to have significantly increased hypothalamic concentrations of neuropeptide Y (NPY), a regulatory peptide that powerfully stimulates eating and drinking and inhibits secretion of several pituitary hormones when injected centrally. Tissue NPY concentrations have been measured by radioimmunoassay in selected hypothalamic regions microdissected from fresh, unfixed brain slices to localize diabetes-associated NPY changes precisely within the hypothalamus. Significant (35-200%) increases in NPY concentrations (P less than .01 vs. matched nondiabetic controls) were found in specific hypothalamic regions between 3 and 14 wk after induction of STZ-D. These regions included the paraventricular and ventromedial nuclei and lateral hypothalamic area, major appetite-regulating areas that are sensitive to the hyperphagic and polydipsic actions of NPY. Increased NPYergic activity in these areas may, at least partly, drive the increased eating and drinking characteristic of STZ-D. NPY concentrations were also increased in the arcuate nucleus and medial preoptic area. Because both of these regions are important in modulating pituitary hormone secretion, local NPY increases may be involved in the impaired secretion of luteinizing hormone, thyroid-stimulating hormone, growth hormone, and prolactin known to occur in STZ-D. Our finding of NPY increases in specific hypothalamic nuclei associated with functional changes found in STZ-D suggests that this peptide may have a role in the altered metabolic and neuroendocrine regulation of the syndrome.

Animals↗
PubMed2001

Effect of intracerebroventricular orexin-B on food intake in sheep.

Orexin is a hypothalamic neuropeptide that regulates feeding behavior in rats. Orexin-B has recently been cloned in pigs and was shown to stimulate food intake after intramuscular injection. This study was designed to determine whether intracerebroventricular (ICV) and intravenous injections of orexin could regulate appetite in sheep. Suffolk wethers were moved to indoor facilities, adapted to diets for 6 wk, and trained to stand in stanchions for 3 to 6 h each day for 2 wk before indwelling ICV cannulas were installed. These sheep were provided water and they consumed feed ad libitum. On the day before an experiment, each sheep was cannulated in a jugular vein. On the day of an experiment, sheep were placed in stanchions and allowed to stand for 1 h before use. Sheep were then monitored over a 2-h control period before i.v. injection with saline or porcine orexin-B (3 micrograms/kg BW) or ICV injection with artificial cerebrospinal fluid (CSF), orexin (0.03, 0.3, or 3 micrograms/kg BW) or in a second experiment with either orexin B (0.03, 0.3, 3 micrograms/kg BW), neuropeptide-Y (NPY; 0.3 microgram/kg BW), or orexin plus NPY. Food intake was monitored for consecutive 2-h periods. The i.v. injections of orexin did not affect food intake or metabolite or hormone concentrations. In ICV sheep, orexin increased food intake at 2 (P < 0.04) and at 4 h (P < 0.02). Food intake was greatest with the 0.3 microgram/kg BW dosage of orexin (P < 0.05). In the first 2 h after injection, orexin had an effect similar to that of NPY (0.23 kg for orexin and 0.2 kg for NPY). The combination of NPY and orexin had a greater effect on food intake (to 0.34 kg) than did either orexin (P < 0.05) or NPY (P < 0.008) alone. Differences were not apparent in the subsequent 2-h interval. No differences were noted in free fatty acid, glucose, growth hormone, luteinizing hormone, or insulin concentrations following orexin injection. There was an effect of ICV orexin treatment on plasma cortisol concentrations (P < 0.002). Cortisol was increased by orexin at the 0- to 2-h (P < 0.008) and in the 2- to 4-h (P < 0.009) intervals after orexin injection. These data indicate that central administration of orexin stimulates feed intake in sheep.

Animals↗
PubMed2005

Effects of short-term feed deprivation and melatonin implants on circadian patterns of leptin in the horse.

Leptin is a protein hormone produced by adipose tissue that influences hypothalamic mechanisms regulating appetite and energy balance. In species tested thus far, including horses, concentrations of leptin increase as animal fat mass increases. The variables and mechanisms that influence the secretion of leptin are not well known, nor is it known in equine species how the secretion of leptin is influenced by acute alterations in energy balance, circadian patterns, and/or reproductive competence. Our objectives were to determine in horses: 1) whether plasma concentrations of leptin are secreted in a circadian and/or a pulsatile pattern; 2) whether a 48-h period of feed restriction would alter plasma concentrations of leptin, growth hormone, or insulin; and 3) whether ovariectomy and/or a melatonin implant would affect leptin. In Exp. 1, mares exposed to ambient photoperiod of visible light (11 h, 33 min to 11 h, 38 min), received treatments consisting of a 48-h feed restriction (RES) or 48 h of alfalfa hay fed ad libitum (FED). Mares were maintained in a dry lot before sampling and were tethered to a rail during sampling. Analyses revealed that leptin was not secreted in a pulsatile manner, and that mean leptin concentrations were greater (P < 0.001) in FED vs. RES mares (17.20 +/- 0.41 vs. 7.29 +/- 0.41 ng/mL). Plasma growth hormone was pulsatile, and mean concentrations were greater in RES than FED mares (2.15 +/- 0.31 vs. 1.08 +/- 0.31 ng/mL; P = 0.05). Circadian patterns of leptin secretion were observed, but only in FED mares (15.39 +/- 0.58 ng/mL for morning vs. 19.00 +/- 0.58 ng/mL for evening; P < 0.001). In Exp. 2, mares that were ovariectomized or intact received either a s.c. melatonin implant or a sham implant. Thereafter, blood was sampled at weekly intervals at 1000 and 1700. Concentrations of leptin in samples collected at 1700 were greater (P < 0.001) than in those collected at 1000 (28.24 +/- 1.7 vs. 22.07 +/- 1.7 ng/mL). Neither ovariectomy nor chronic treatment with melatonin affected plasma concentrations of leptin or the circadian pattern of secretion. These data provide evidence that plasma leptin concentrations in the equine are sensitive to acute changes in nutritional status and vary in a circadian pattern that is sensitive to fasting but not to melatonin treatment or ovariectomy.

Animals↗