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Liyanagamage DSNK, McColl LK, Glasgow LNM, Levine AS, Olszewski PK. Effect of intranasal oxytocin on palatable food consumption and c-Fos immunoreactivity in relevant brain areas in rats. Physiol Behav 2023; 271:114318. [PMID: 37543105 DOI: 10.1016/j.physbeh.2023.114318] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2023] [Revised: 08/01/2023] [Accepted: 08/02/2023] [Indexed: 08/07/2023]
Abstract
Peripheral and central injections of oxytocin (OT) in laboratory animals decrease eating for energy and palatability, but the hypophagic response is dependent on the administration route. Human studies rely on intranasal (IN) administration of the peptide, the route underutilized in OT animal feeding studies thus far. Therefore, we examined the effect of IN OT on various aspects of food consumption in rats: (a) overnight deprivation-induced standard chow intake, (b) episodic (2-h) consumption of calorie-dense and palatable high-fat high-sugar (HFHS) chow, (c) 2-h episodic intake of palatable and calorie-dilute sucrose and Intralipid solutions, and (d) 2-h sucrose solution intake in rats habituated to ingesting this solution daily for several weeks. Finally, we assessed c-Fos changes in response to the acute IN OT administration in rats habituated to daily sugar consumption. We found that IN 20μg OT decreased deprivation-induced intake of standard chow and HFHS chow in nondeprived rats without affecting water consumption. IN OT also reduced 2-hour episodic fluid consumption of sucrose, but not Intralipid. In the habitual sugar consumption paradigm, acute IN OT diminished sucrose solution intake in animals accustomed to the 2-hour/day sucrose meal regimen. In rats habitually consuming sucrose, IN OT altered c-Fos immunoreactivity in brain areas related to energy homeostasis and reward, including the central nucleus of the amygdala, the hypothalamic paraventricular and the arcuate nuclei. We conclude that IN OT is an effective appetite suppressant for carbohydrate/sugar diets in rats and its effects involve feeding-related brain circuits.
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Affiliation(s)
| | - Laura K McColl
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand
| | - Lisa N M Glasgow
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, United States of America
| | - Pawel K Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand; Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, United States of America; Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN 55414, United States of America.
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2
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Abstract
The four-tiered NOVA food classification defines foods based on their degree of processing and ranges from native unprocessed foods to so-called "ultra-processed" foods. Recent publications have suggested that foods classified as ultra-processed are unhealthy and contribute to the obesity epidemic. It is important to distinguish between formulation and processing of a food. In most cases it is the formulation more than the processing that results in foods that are not recommended as part of a healthy diet. Such "ultra-formulated" foods are unhealthy because they are high in added sugar and other caloric sweeteners, refined flours saturated fats and salt to increase palatability. The understanding that processing and formulation are distinct will assist health professionals in identifying the types of foods that are unhealthy and contribute to overconsumption and obesity. It furthermore will help to destigmatize food technology and promote discussions amongst health professionals, food scientists, corporate scientists, government officials and the general public. Novel food processing techniques are urgently needed in times of population growth, climate change and war-induced food shortages.
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Affiliation(s)
- Allen S. Levine
- Department of Food Science and Nutrition University of Minnesota 1334 Eckles Avenue St. Paul MN55108 United States
| | - Job Ubbink
- Department of Food Science and Nutrition University of Minnesota 1334 Eckles Avenue St. Paul MN55108 United States
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Levine AS, Jewett DC, Kotz CM, Olszewski PK. Behavioral plasticity: Role of neuropeptides in shaping feeding responses. Appetite 2022; 174:106031. [PMID: 35395362 DOI: 10.1016/j.appet.2022.106031] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2021] [Revised: 03/12/2022] [Accepted: 03/29/2022] [Indexed: 11/28/2022]
Abstract
Behavioral plasticity refers to changes occurring due to external influences on an organism, including adaptation, learning, memory and enduring influences from early life experience. There are 2 types of behavioral plasticity: "developmental", which refers to gene/environment interactions affecting a phenotype, and "activational" which refers to innate physiology and can involve structural physiological changes of the body. In this review, we focus on feeding behavior, and studies involving neuropeptides that influence behavioral plasticity - primarily opioids, orexin, neuropeptide Y, and oxytocin. In each section of the review, we include examples of behavioral plasticity as it relates to actions of these neuropeptides. It can be concluded from this review that eating behavior is influenced by a number of external factors, including time of day, type of food available, energy balance state, and stressors. The reviewed work underscores that environmental factors play a critical role in feeding behavior and energy balance, but changes in eating behavior also result from a multitude of non-environmental factors, such that there can be no single mechanism or variable that can explain ingestive behavior.
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Affiliation(s)
- Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, 55113, USA.
| | - David C Jewett
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI, USA
| | - Catherine M Kotz
- Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN, 55414, USA; Geriatric, Research, Education and Clinical Center, Minneapolis Veterans Affairs Health, Minneapolis, MN, 55417, USA
| | - Pawel K Olszewski
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, 55113, USA; Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN, 55414, USA; Faculty of Science and Engineering, University of Waikato, Hamilton, 3240, New Zealand
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Jewett DC, Liyanagamage DSNK, Avond MAV, Anderson MAB, Twaroski KA, Marek MA, James KF, Pal T, Klockars A, Olszewski PK, Levine AS. Chronic Intermittent Sucrose Consumption Facilitates the Ability to Discriminate Opioid Receptor Blockade with Naltrexone in Rats. Nutrients 2022; 14:nu14050926. [PMID: 35267900 PMCID: PMC8912831 DOI: 10.3390/nu14050926] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 02/15/2022] [Accepted: 02/18/2022] [Indexed: 12/20/2022] Open
Abstract
The opioid antagonist naltrexone (NTX) decreases intake of preferred diets in rats at very low doses relative to doses needed to decrease intake of "bland" laboratory chow. In the absence of an opioid agonist, NTX is not discriminable using operant techniques. In the current study, we found that rats given intermittent access to a 25% sucrose solution learned to discriminate between various naltrexone doses and saline. None of the rats given only water learned to discriminate between naltrexone and saline. When access to the sucrose solution was discontinued for 14 days, the rats lost the ability to discriminate between NTX and saline. We also studied the changes of c-Fos IR in selected brain regions in rats treated with saline versus NTX that were drinking water or 25% sucrose. An injection of NTX or saline resulted in a significant drug, diet, and interaction effect in various brain regions associated with feeding behavior, particularly the amygdala, accumbens, and hypothalamic sites. Thus, we found that ingestion of a sucrose solution results in the ability of rats to reliably discriminate naltrexone administration. In addition, sucrose and naltrexone altered c-Fos IR in an interactive fashion in brain regions known to be involved in ingestion behavior.
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Affiliation(s)
- David C. Jewett
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Donisha S. N. K. Liyanagamage
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand; (D.S.N.K.L.); (T.P.); (A.K.); (P.K.O.)
| | - Mark A. Vanden Avond
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Molly A. B. Anderson
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Kyleigh A. Twaroski
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Morgan A. Marek
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Kimberly F. James
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI 54701, USA; (D.C.J.); (M.A.V.A.); (M.A.B.A.); (K.A.T.); (M.A.M.); (K.F.J.)
| | - Tapasya Pal
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand; (D.S.N.K.L.); (T.P.); (A.K.); (P.K.O.)
| | - Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand; (D.S.N.K.L.); (T.P.); (A.K.); (P.K.O.)
| | - Pawel K. Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand; (D.S.N.K.L.); (T.P.); (A.K.); (P.K.O.)
- Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN 55414, USA
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA
| | - Allen S. Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA
- Correspondence:
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Head MA, McColl LK, Klockars A, Levine AS, Olszewski PK. Acute Hypophagia and Changes in c-Fos Immunoreactivity in Adolescent Rats Treated with Low Doses of Oxytocin and Naltrexone. J Clin Med 2021; 11:jcm11010059. [PMID: 35011797 PMCID: PMC8745073 DOI: 10.3390/jcm11010059] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 12/14/2021] [Accepted: 12/20/2021] [Indexed: 01/19/2023] Open
Abstract
A recent case report has shown that an adjunctive oxytocin + naltrexone (OT + NTX) treatment promoted more robust hypophagia and body weight reduction than OT alone in an adolescent male with hypothalamic obesity after craniopharyngioma resection. Thus far, there has been no basic research in adolescent laboratory animals that would examine whether the benefit of OT + NTX on appetite extends onto adolescent individuals without surgically induced overeating. Thus, here we examined whether low doses of combined OT + NTX acutely affect post-deprivation intake of energy-dense, standard chow; intake of energy-dense and palatable high-fat high-sugar (HFHS) diet; or calorie-dilute, palaTable 10% sucrose solution without deprivation in adolescent male rats. We assessed whether OT + NTX decreases water intake after water deprivation or produces a conditioned taste aversion (CTA). Finally, by using c-Fos immunoreactivity, we determined changes in activity of feeding-related brain areas after OT + NTX. We found that individual subthreshold doses of OT and NTX decreased feeding induced by energy and by palatability. Significant c-Fos changes were noted in the arcuate and dorsomedial hypothalamic nuclei. The hypophagic doses of OT + NTX did not suppress water intake in thirsty rats and did not cause a CTA, which suggests that feeding reduction is not a secondary effect of gastrointestinal discomfort or changes in thirst processing. We conclude that OT + NTX is an effective drug combination to reduce appetite in adolescent male rats.
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Affiliation(s)
- Mitchell A. Head
- Faculty of Science and Engineering, University of Waikato, Hamilton 3214, New Zealand; (M.A.H.); (L.K.M.); (A.K.)
| | - Laura K. McColl
- Faculty of Science and Engineering, University of Waikato, Hamilton 3214, New Zealand; (M.A.H.); (L.K.M.); (A.K.)
| | - Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton 3214, New Zealand; (M.A.H.); (L.K.M.); (A.K.)
| | - Allen S. Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55113, USA;
| | - Pawel K. Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton 3214, New Zealand; (M.A.H.); (L.K.M.); (A.K.)
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55113, USA;
- Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN 55416, USA
- Correspondence:
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Klockars A, Pal T, Levine AS, Olszewski PK. Neural Basis of Dysregulation of Palatability-Driven Appetite in Autism. Curr Nutr Rep 2021; 10:391-398. [PMID: 34417997 DOI: 10.1007/s13668-021-00368-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 07/01/2021] [Indexed: 11/30/2022]
Abstract
PURPOSE OF REVIEW In research on autism spectrum disorder (ASD), cognitive, speech- and anxiety-related impairments have been the focus of the majority of studies. One consistently reported ASD symptom that has rarely attracted attention is disordered appetite. The goal of this paper is to assess whether ASD-related dysregulation of food intake impacts consumption of palatable foods, including sugar. RECENT FINDINGS Aberrant neural processing at the reward system level is at least partially responsible for excessive intake of palatable tastants, including sugar. Impaired oxytocin (OT) signaling likely contributes to the magnitude of this overconsumption. Since intake for reward is generally elevated in individuals with ASD, one strategy to curb sugar overconsumption might utilize presentation of alternative palatable food choices that are more nutritionally adequate than sucrose. Furthermore, OT, which is clinically tested to alleviate other ASD symptoms, might be an effective tool to curb overconsumption of sugar, as well as - likely - of other excessively ingested palatable foods, especially those that have sweet taste.
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Affiliation(s)
- Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Tapasya Pal
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, USA.
| | - Pawel K Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand.,Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN, USA.,Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, USA
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7
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Head MA, Levine AS, Christian DG, Klockars A, Olszewski PK. Effect of combination of peripheral oxytocin and naltrexone at subthreshold doses on food intake, body weight and feeding-related brain gene expression in male rats. Physiol Behav 2021; 238:113464. [PMID: 34022256 DOI: 10.1016/j.physbeh.2021.113464] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2020] [Revised: 05/17/2021] [Accepted: 05/18/2021] [Indexed: 01/17/2023]
Abstract
In a recent case report involving a male with hypothalamic obesity, concurrent administration of oxytocin (OT) and an opioid receptor antagonist, naltrexone (NTX), synergistically affected energy balance. Here, by using laboratory rats, we examined whether the reported synergy between OT and NTX in the context of food intake extends beyond that one unique case. We found that intravenous OT+NTX combination, at doses subthreshold for each of the drugs individually, decreased episodic consumption of a 10% sucrose solution in non-deprived animals. Daily administration of OT and NTX just before a scheduled, 2-hour, high-fat high-sugar (HFHS) meal over 24 days, decreased cumulative HFHS diet intake, but without a change in body weight due to compensatory standard chow intake during the remainder of the day. The NTX-OT treatment affected expression of several feeding-related genes in the hypothalamus, brain stem and nucleus accumbens, brain regions essential for the regulation of energy- and reward-driven consumption. We conclude that OT and NTX act synergistically to decrease food consumption in rats and that this transient effect is accompanied by changes in brain processes relevant to feeding.
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Affiliation(s)
- Mitchell A Head
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, 55113 United States.
| | - David G Christian
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Anica Klockars
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Pawel K Olszewski
- School of Science, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand; Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, 55113 United States; Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, MN, United States
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Klockars A, Levine AS, Head MA, Perez-Leighton CE, Kotz CM, Olszewski PK. Impact of Gut and Metabolic Hormones on Feeding Reward. Compr Physiol 2021; 11:1425-1447. [PMID: 33577129 DOI: 10.1002/cphy.c190042] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Ingestion of food activates a cascade of endocrine responses (thereby reflecting a contemporaneous feeding status) that include the release of hormones from the gastrointestinal (GI) tract, such as cholecystokinin (CCK), glucagonlike peptide YY (PYY), peptide PP, and oleoylethanolamide, as well as suppression of ghrelin secretion. The pancreas and adipose tissue, on the other hand, release hormones that serve as a measure of the current metabolic state or the long-term energy stores, that is, insulin, leptin, and adiponectin. It is well known and intuitively understandable that these hormones target either directly (by crossing the blood-brain barrier) or indirectly (e.g., via vagal input) the "homeostatic" brainstem-hypothalamic pathways involved in the regulation of appetite. The current article focuses on yet another target of the metabolic and GI hormones that is critical in inducing changes in food intake, namely, the reward system. We discuss the physiological basis of this functional interaction, its importance in the control of appetite, and the impact that disruption of this crosstalk has on energy intake in select physiological and pathophysiological states. We conclude that metabolic and GI hormones have a capacity to strengthen or weaken a response of the reward system to a given food, and thus, they are fundamental in ensuring that feeding reward is plastic and dependent on the energy status of the organism. © 2021 American Physiological Society. Compr Physiol 11:1425-1447, 2021.
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Affiliation(s)
- Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA
| | - Mitchell A Head
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | | | - Catherine M Kotz
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA.,Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, Minnesota, USA
| | - Pawel K Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand.,Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA.,Department of Integrative Biology and Physiology, Medical School, University of Minnesota, Minneapolis, Minnesota, USA
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Jewett DC, Klockars A, Smith TR, Brunton C, Head MA, Tham RL, Kwilasz AJ, Hahn TW, Wiebelhaus JM, Ewan EE, Carroll RM, Grace MK, Levine AS, Olszewski PK. Effects of opioid receptor ligands in rats trained to discriminate 22 from 2 hours of food deprivation suggest a lack of opioid involvement in eating for hunger. Behav Brain Res 2020; 380:112369. [DOI: 10.1016/j.bbr.2019.112369] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2019] [Revised: 10/28/2019] [Accepted: 11/15/2019] [Indexed: 10/25/2022]
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Klockars A, Wood EL, Gartner SN, McColl LK, Levine AS, Carpenter EA, Prosser CG, Olszewski PK. Palatability of Goat's versus Cow's Milk: Insights from the Analysis of Eating Behavior and Gene Expression in the Appetite-Relevant Brain Circuit in Laboratory Animal Models. Nutrients 2019; 11:nu11040720. [PMID: 30925727 PMCID: PMC6520687 DOI: 10.3390/nu11040720] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2019] [Revised: 03/17/2019] [Accepted: 03/25/2019] [Indexed: 01/20/2023] Open
Abstract
Goat's (GM) and cow's milk (CM) are dietary alternatives with select health benefits shown in human and animal studies. Surprisingly, no systematic analysis of palatability or preference for GM vs. CM has been performed to date. Here, we present a comprehensive investigation of short-term intake and palatability profiles of GM and CM in laboratory mice and rats. We studied consumption in no-choice and choice scenarios, including meal microstructure, and by using isocaloric milks and milk-enriched solid diets. Feeding results are accompanied by qPCR data of relevant genes in the energy balance-related hypothalamus and brain stem, and in the nucleus accumbens, which regulates eating for palatability. We found that GM and CM are palatable to juvenile, adult, and aged rodents. Given a choice, animals prefer GM- to CM-based diets. Analysis of meal microstructure using licking patterns points to enhanced palatability of and, possibly, greater motivation toward GM over CM. Most profound changes in gene expression after GM vs. CM were associated with the brain systems driving consumption for reward. We conclude that, while both GM and CM are palatable, GM is preferred over CM by laboratory animals, and this preference is driven by central mechanisms controlling eating for pleasure.
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Affiliation(s)
- Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
| | - Erin L Wood
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
| | - Sarah N Gartner
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
| | - Laura K McColl
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55113, USA.
| | | | - Colin G Prosser
- Dairy Goat Cooperative (NZ) Ltd., Hamilton 3206, New Zealand.
| | - Pawel K Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton 3240, New Zealand.
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55113, USA.
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Head MA, Jewett DC, Gartner SN, Klockars A, Levine AS, Olszewski PK. Effect of Oxytocin on Hunger Discrimination. Front Endocrinol (Lausanne) 2019; 10:297. [PMID: 31156549 PMCID: PMC6529581 DOI: 10.3389/fendo.2019.00297] [Citation(s) in RCA: 16] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/27/2019] [Accepted: 04/25/2019] [Indexed: 12/28/2022] Open
Abstract
Centrally and peripherally administered oxytocin (OT) decreases food intake and activation of the endogenous OT systems, which is associated with termination of feeding. Evidence gathered thus far points to OT as a facilitator of early satiation, a peptide that reduces the need for a meal that has already begun. It is not known, however, whether OT can diminish a feeling of hunger, thereby decreasing a perceived need to seek calories. Therefore, in the current project, we first confirmed that intraperitoneal (i.p.) OT at 0.3-1 mg/kg reduces food intake in deprived and non-deprived rats. We then used those OT doses in a unique hunger discrimination protocol. First, rats were trained to discriminate between 22- and 2-h food deprivation (hungry vs. sated state) in a two-lever operant procedure. After rats acquired the discrimination, they were food-restricted for 22 h and given i.p. OT before a generalization test session. OT did not decrease 22-h deprivation-appropriate responding to match that following 2-h food deprivation, thus, it did not reduce the perceived level of hunger. In order to better understand the mechanisms behind this ineffectiveness of OT, we used c-Fos immunohistochemistry to determine whether i.p. OT activates a different subset of feeding-related brain sites under 22- vs. 2-h deprivation. We found that in sated animals, OT induces c-Fos changes in a broader network of hypothalamic and brain stem sites compared to those affected in the hungry state. Finally, by employing qPCR analysis, we asked whether food deprivation vs. sated state have an impact on OT receptor expression in the brain stem, a CNS "entry" region for peripheral OT. Fasted animals had significantly lower OT receptor mRNA levels than their ad libitum-fed counterparts. We conclude that OT does not diminish a feeling of hunger before a start of a meal. Instead OT's anorexigenic properties are manifested once consumption has already begun which is-at least to some extent-driven by changes in brain responsiveness to OT treatment in the hungry vs. fed state. OT should be viewed as a mediator of early satiation rather than as a molecule that diminishes perceived hunger.
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Affiliation(s)
- Mitchell A. Head
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - David C. Jewett
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI, United States
| | - Sarah N. Gartner
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Anica Klockars
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Allen S. Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, United States
| | - Pawel K. Olszewski
- Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, United States
- *Correspondence: Pawel K. Olszewski
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Opichka K, Smith C, Levine AS. Problematic Eating Behaviors Are More Prevalent in African American Women Who Are Overweight or Obese Than African American Women Who Are Lean or Normal Weight. Fam Community Health 2019; 42:81-89. [PMID: 30768472 DOI: 10.1097/fch.0000000000000222] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Problematic eating behaviors such as overeating and loss of control over consumption can lead to obesity. Problematic eating behaviors among women of differing body mass indexes were explored through focus group methodology, the Palatable Eating Motives Scale (PEMS), and a taste test in a sample of low-income African American women (n = 45). Women who were overweight or obese (W-O/O) reported more problematic eating behaviors including eating in the absence of hunger, frequent overeating, and increased food thoughts than women who were lean or normal weight (W-L/N). The W-O/O appear to possess more problematic eating behaviors than W-L/N.
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Affiliation(s)
- Katelyn Opichka
- Department of Food Science and Nutrition, University of Minnesota, St Paul
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Gartner SN, Aidney F, Klockars A, Prosser C, Carpenter EA, Isgrove K, Levine AS, Olszewski PK. Intragastric preloads of l-tryptophan reduce ingestive behavior via oxytocinergic neural mechanisms in male mice. Appetite 2018; 125:278-286. [PMID: 29471071 DOI: 10.1016/j.appet.2018.02.015] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/29/2017] [Revised: 02/09/2018] [Accepted: 02/15/2018] [Indexed: 11/29/2022]
Abstract
Human and laboratory animal studies suggest that dietary supplementation of a free essential amino acid, l-tryptophan (TRP), reduces food intake. It is unclear whether an acute gastric preload of TRP decreases consumption and whether central mechanisms underlie TRP-driven hypophagia. We examined the effect of TRP administered via intragastric gavage on energy- and palatability-induced feeding in mice. We sought to identify central mechanisms through which TRP suppresses appetite. Effects of TRP on consumption of energy-dense and energy-dilute tastants were established in mice stimulated to eat by energy deprivation or palatability. A conditioned taste aversion (CTA) paradigm was used to assess whether hypophagia is unrelated to sickness. c-Fos immunohistochemistry was employed to detect TRP-induced activation of feeding-related brain sites and of oxytocin (OT) neurons, a crucial component of satiety circuits. Also, expression of OT mRNA was assessed with real-time PCR. The functional importance of OT in mediating TRP-driven hypophagia was substantiated by showing the ability of OT receptor blockade to abolish TRP-induced decrease in feeding. TRP reduced intake of energy-dense standard chow in deprived animals and energy-dense palatable chow in sated mice. Anorexigenic doses of TRP did not cause a CTA. TRP failed to affect intake of palatable yet calorie-dilute or noncaloric solutions (10% sucrose, 4.1% Intralipid or 0.1% saccharin) even for TRP doses that decreased water intake in thirsty mice. Fos analysis revealed that TRP increases activation of several key feeding-related brain areas, especially in the brain stem and hypothalamus. TRP activated hypothalamic OT neurons and increased OT mRNA levels, whereas pretreatment with an OT antagonist abolished TRP-driven hypophagia. We conclude that intragastric TRP decreases food and water intake, and TRP-induced hypophagia is partially mediated via central circuits that encompass OT.
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Affiliation(s)
| | | | | | - Colin Prosser
- Dairy Goat Co-operative (NZ) Ltd, Hamilton, New Zealand
| | | | | | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, USA
| | - Pawel K Olszewski
- University of Waikato, Hamilton, New Zealand; Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN, USA.
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15
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Klockars OA, Waas JR, Klockars A, Levine AS, Olszewski PK. Neural Basis of Ventromedial Hypothalamic Oxytocin-Driven Decrease in Appetite. Neuroscience 2017; 366:54-61. [DOI: 10.1016/j.neuroscience.2017.10.008] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Revised: 10/05/2017] [Accepted: 10/06/2017] [Indexed: 02/03/2023]
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Abstract
PURPOSE OF REVIEW Laboratory animal experiments have consistently shown that oxytocin causes early termination of food intake, thereby promoting a decrease in body weight in a long term. Recent studies have also assessed some of oxytocin's effects on appetite and energy balance in humans. The present study examines the findings of the key basic research and of the few clinical studies published thus far in the context of potential benefits and challenges stemming from the use of oxytocin in obese patients. RECENT FINDINGS Basic research indicates the involvement of oxytocin in satiety, processing, in reducing a drive to eat for pleasure and because of psychosocial factors. Although the results of clinical studies are very scarce, they suggest that oxytocin administered intranasally in humans decreases energy-induced and reward-induced eating, supports cognitive control of food choices, and improves glucose homeostasis, and its effectiveness may be BMI dependent. SUMMARY Despite the wealth of basic research showing broad anorexigenic effects of oxytocin, clinical studies on oxytocin's therapeutic potential in obesity, are still in their infancy. Future implementation of oxytocin-based pharmacological strategies in controlling energy balance will likely depend on our ability to integrate diverse behavioral and metabolic effects of oxytocin in obesity treatment regimens.
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Affiliation(s)
- Pawel K Olszewski
- aDepartment of Food Science and Nutrition, University of Minnesota, St Paul, Minnesota, USA bDepartment of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
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Klockars A, Brunton C, Li L, Levine AS, Olszewski PK. Intravenous administration of oxytocin in rats acutely decreases deprivation-induced chow intake, but it fails to affect consumption of palatable solutions. Peptides 2017; 93:13-19. [PMID: 28460894 DOI: 10.1016/j.peptides.2017.04.010] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/24/2016] [Revised: 04/22/2017] [Accepted: 04/27/2017] [Indexed: 01/03/2023]
Abstract
Despite its limited ability to cross the blood-brain barrier, peripherally administered oxytocin (OT) acutely decreases food intake, most likely via the brainstem and hypothalamic mechanisms. Studies performed to date have focused mainly on the effects of subcutaneous or intraperitoneal OT on the consumption of only solid calorie-dense diets (either standard or high-fat), whereas it is unknown whether, similarly to central OT, peripherally administered peptide reduces intake of calorie-dilute and non-caloric palatable solutions. In this project, we established that 0.1μg/kg intravenous (IV) OT is the lowest anorexigenic dose, decreasing deprivation-induced standard chow intake by ca. 40% in rats and its effect does not stem from aversion. We then used this dose in paradigms in which effects of centrally acting OT ligands on consumption of palatable solutions had been previously reported. We found that IV OT did not change episodic intake of individually presented palatable solutions containing 10% sucrose, 0.1% saccharin, combined 10% sucrose-0.1% saccharin or 4.1%. Intralipid and it failed to affect daily scheduled consumption of a sucrose solution in non-deprived rats. In a two-bottle choice test, IV OT did not shift animals' preference from sucrose to Intralipid. Finally, OT injected IV prior to the simultaneous presentation chow and a sucrose solution in food-deprived rats significantly decreased chow intake, whereas sugar water consumption remained unchanged. We conclude that IV OT reduces deprivation-induced chow intake without causing aversion, but the dose effective in decreasing energy-driven consumption of high-calorie food fails to affect consumption of palatable calorie-dilute solutions.
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Affiliation(s)
- Anica Klockars
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Chloe Brunton
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - Lu Li
- University of Auckland, Waikato Clinical School, Hamilton, 3240 New Zealand
| | - Allen S Levine
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA
| | - Pawel K Olszewski
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand; Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA.
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18
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Olszewski PK, Levine AS. Basic research on appetite regulation: Social context of a meal is missing. Pharmacol Biochem Behav 2016; 148:106-7. [DOI: 10.1016/j.pbb.2016.06.009] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2016] [Accepted: 06/28/2016] [Indexed: 10/21/2022]
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Affiliation(s)
- Saverio Cinti
- University of Ancona, School of Medicine , Ancona, Italy
| | - John T Garretson
- Georgia State University Neuroscience InstituteCenter for Obesity Reversal , Atlanta, GA, USA
| | - Harvey J Grill
- University of Pennsylvania, Department of Psychology , Philadelphia, PA, USA
| | - Allen S Levine
- University of Minnesota , Morrill Hall (Room 110) 100 Church Street , Minneapolis, MN 55455, USA
| | - Paul Trayhurn
- University of Liverpool, Obesity Biology Research Unit, Liverpool, UK & University of BuckinghamBuckingham Institute for Translational Medicine , Buckingham, UK
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20
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Herisson FM, Waas JR, Fredriksson R, Schiöth HB, Levine AS, Olszewski PK. Oxytocin Acting in the Nucleus Accumbens Core Decreases Food Intake. J Neuroendocrinol 2016; 28. [PMID: 27114001 DOI: 10.1111/jne.12381] [Citation(s) in RCA: 74] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/27/2015] [Revised: 01/29/2016] [Accepted: 02/24/2016] [Indexed: 01/15/2023]
Abstract
Central oxytocin (OT) promotes feeding termination in response to homeostatic challenges, such as excessive stomach distension, salt loading and toxicity. OT has also been proposed to affect feeding reward by decreasing the consumption of palatable carbohydrates and sweet tastants. Because the OT receptor (OTR) is expressed in the nucleus accumbens core (AcbC) and shell (AcbSh), a site regulating diverse aspects of eating behaviour, we investigated whether OT acts there to affect appetite in rats. First, we examined whether direct AcbC and AcbSh OT injections affect hunger- and palatability-driven consumption. We found that only AcbC OT infusions decrease deprivation-induced chow intake and reduce the consumption of palatable sucrose and saccharin solutions in nondeprived animals. These effects were abolished by pretreatment with an OTR antagonist, L-368,899, injected in the same site. AcbC OT at an anorexigenic dose did not induce a conditioned taste aversion, which indicates that AcbC OT-driven anorexia is not caused by sickness/malaise. The appetite-specific effect of AcbC OT is supported by the real-time polymerase chain reaction analysis of OTR mRNA in the AcbC, which revealed that food deprivation elevates OTR mRNA expression, whereas saccharin solution intake decreases OTR transcript levels. We also used c-Fos immunohistochemistry as a marker of neuronal activation and found that AcbC OT injection increases activation of the AcbC itself, as well as of two feeding-related sites: the hypothalamic paraventricular and supraoptic nuclei. Finally, considering the fact that OT plays a significant role in social behaviour, we examined whether offering animals a meal in a social setting would modify their hypophagic response to AcbC OT injections. We found that a social context abolishes the anorexigenic effects of AcbC OT. We conclude that OT acting via the AcbC decreases food intake driven by hunger and reward in rats offered a meal in a nonsocial setting.
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Affiliation(s)
- F M Herisson
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - J R Waas
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
| | - R Fredriksson
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - H B Schiöth
- Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - A S Levine
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA
| | - P K Olszewski
- Department of Biological Sciences, Faculty of Science and Engineering, University of Waikato, Hamilton, New Zealand
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA
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Olszewski PK, Klockars A, Levine AS. Oxytocin: A Conditional Anorexigen whose Effects on Appetite Depend on the Physiological, Behavioural and Social Contexts. J Neuroendocrinol 2016; 28. [PMID: 26918919 DOI: 10.1111/jne.12376] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Revised: 02/16/2016] [Accepted: 02/19/2016] [Indexed: 01/17/2023]
Abstract
Central oxytocin suppresses appetite. Neuronal activity and the release of oxytocin coincide with satiation, as well as with adverse events (e.g. hyperosmolality, toxicity or excessive stomach distension) that necessitate an immediate termination of eating behaviour. Oxytocin also decreases consumption driven by reward, especially as derived from ingesting carbohydrates and sweet tastants. This review summarises current knowledge of the role of oxytocin in food intake regulation and highlights a growing body of evidence showing that oxytocin is a conditional anorexigen [i.e. its effects on appetite differ significantly with respect to certain (patho)physiological, behavioural and social contexts].
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Affiliation(s)
- P K Olszewski
- Department of Biological Sciences, University of Waikato, Hamilton, New Zealand
| | - A Klockars
- Department of Biological Sciences, University of Waikato, Hamilton, New Zealand
| | - A S Levine
- Department of Food Science and Nutrition, University of Minnesota, St Paul, MN, USA
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22
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Grill HJ, Levine AS. Tim Bartness, Ph.D. (1953-2015). Obesity (Silver Spring) 2015; 23:2315-6. [PMID: 26523830 DOI: 10.1002/oby.21373] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/05/2015] [Accepted: 10/05/2015] [Indexed: 11/06/2022]
Affiliation(s)
- Harvey J Grill
- College of Arts and Science, University of Pennsylvania, Philadelphia, USA
| | - Allen S Levine
- College of Food, Agricultural and Natural Resource Sciences, Department of Food Science and Nutrition, University of Minnesota, St. Paul, Minnesota, USA
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23
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Olszewski PK, Allen K, Levine AS. Effect of oxytocin receptor blockade on appetite for sugar is modified by social context. Appetite 2015; 86:81-7. [DOI: 10.1016/j.appet.2014.10.007] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2014] [Revised: 09/23/2014] [Accepted: 10/13/2014] [Indexed: 01/28/2023]
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Singh A, Dirain ML, Wilczynski A, Chen C, Gosnell BA, Levine AS, Edison AS, Haskell-Luevano C. Synthesis, biophysical, and pharmacological evaluation of the melanocortin agonist AST3-88: modifications of peptide backbone at Trp 7 position lead to a potent, selective, and stable ligand of the melanocortin 4 receptor (MC4R). ACS Chem Neurosci 2014; 5:1020-31. [PMID: 25141170 PMCID: PMC4198065 DOI: 10.1021/cn5000953] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
![]()
The
melanocortin-3 (MC3R) and melanocortin-4 (MC4R) receptors are
expressed in the brain and are implicated in the regulation of food
intake and energy homeostasis. The endogenous agonist ligands for
these receptors (α-, β-, γ-MSH and ACTH) are linear
peptides with limited receptor subtype selectivity and metabolic stability,
thus minimizing their use as probes to characterize the overlapping
pharmacological and physiological functions of the melanocortin receptor
subtypes. In the present study, an engineered template, in which the
peptide backbone was modified by a heterocyclic reverse turn mimetic
at the Trp7 residue, was synthesized using solid phase
peptide synthesis and characterized by a β-galactosidase cAMP
based reporter gene assay. The functional assay identified a ∼5
nM mouse MC4R agonist (AST3-88) with more than 50-fold selectivity
over the mMC3R. Biophysical studies (2D 1H NMR spectroscopy
and molecular dynamics) of AST3-88 identified a type VIII β-turn
secondary structure spanning the pharmacophore domain stabilized by
the intramolecular interactions between the side chains of the His
and Trp residues. Enzymatic studies of AST3-88 revealed enhanced stability
of AST3-88 over the α-MSH endogenous peptide in rat serum. Upon
central administration of AST3-88 into rats, a decreased food intake
response was observed. This is the first study to probe the in vivo
physiological activity of this engineered peptide-heterocycle template.
These findings advance the present knowledge of pharmacophore design
for potent, selective, and metabolically stable melanocortin ligands.
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Affiliation(s)
- Anamika Singh
- Department
of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
| | | | | | | | | | | | | | - Carrie Haskell-Luevano
- Department
of Medicinal Chemistry, University of Minnesota, Minneapolis, Minnesota 55455, United States
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25
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Alsiö J, Rask-Andersen M, Chavan RA, Olszewski PK, Levine AS, Fredriksson R, Schiöth HB. Exposure to a high-fat high-sugar diet causes strong up-regulation of proopiomelanocortin and differentially affects dopamine D1 and D2 receptor gene expression in the brainstem of rats. Neurosci Lett 2014; 559:18-23. [DOI: 10.1016/j.neulet.2013.11.008] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2013] [Revised: 11/01/2013] [Accepted: 11/11/2013] [Indexed: 11/28/2022]
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Olszewski PK, Waas JR, Brooks LL, Herisson F, Levine AS. Oxytocin receptor blockade reduces acquisition but not retrieval of taste aversion and blunts responsiveness of amygdala neurons to an aversive stimulus. Peptides 2013; 50:36-41. [PMID: 24063812 DOI: 10.1016/j.peptides.2013.09.008] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2013] [Revised: 09/13/2013] [Accepted: 09/13/2013] [Indexed: 10/26/2022]
Abstract
When gastrointestinal sickness induced by toxin injection is associated with exposure to novel food, the animal acquires a conditioned taste aversion (CTA). Malaise is accompanied by a surge in oxytocin release and in oxytocin neuronal activity; however, it is unclear whether oxytocin is a key facilitator of aversion or merely its marker. Herein we investigated whether blockade of the oxytocin receptor with the blood-brain barrier penetrant oxytocin receptor antagonist L-368,899 is detrimental for the acquisition and/or retrieval of lithium chloride (LiCl)-dependent CTA to a saccharin solution in mice. We also examined whether L-368,899 given prior to LiCl affects neuronal activity defined through c-Fos immunohistochemistry in select brain sites facilitating CTA acquisition. L-368,899 given prior to LiCl caused a 30% increase in saccharin solution intake in a two-bottle test, but when the antagonist was administered before the two-bottle test, it failed to diminish the retrieval of an existing CTA. LiCl administration increased c-Fos expression in the hypothalamic paraventricular and supraoptic nuclei, area postrema, nucleus of the solitary tract and basolateral and central (CNA) nuclei of the amygdala. L-368,899 injected before LiCl reduced the number of c-Fos positive CNA neurons and brought it down to levels similar to those observed in mice treated only with L-368,899. We conclude that oxytocin is one of the key components in acquisition of LiCl-induced CTA and the aversive response can be alleviated by the oxytocin receptor blockade. Oxytocin receptor antagonism blunts responsiveness of CNA to peripherally injected LiCl.
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Affiliation(s)
- Pawel K Olszewski
- Department of Biological Sciences, University of Waikato, Hamilton 3240, New Zealand; Minnesota Obesity Center, St. Paul, MN 55117, USA.
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Stice E, Figlewicz DP, Gosnell BA, Levine AS, Pratt WE. The contribution of brain reward circuits to the obesity epidemic. Neurosci Biobehav Rev 2012; 37:2047-58. [PMID: 23237885 DOI: 10.1016/j.neubiorev.2012.12.001] [Citation(s) in RCA: 176] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2012] [Revised: 11/21/2012] [Accepted: 12/03/2012] [Indexed: 12/22/2022]
Abstract
One of the defining characteristics of the research of Ann E. Kelley was her recognition that the neuroscience underlying basic learning and motivation processes also shed significant light upon mechanisms underlying drug addiction and maladaptive eating patterns. In this review, we examine the parallels that exist in the neural pathways that process both food and drug reward, as determined by recent studies in animal models and human neuroimaging experiments. We discuss contemporary research that suggests that hyperphagia leading to obesity is associated with substantial neurochemical changes in the brain. These findings verify the relevance of reward pathways for promoting consumption of palatable, calorically dense foods, and lead to the important question of whether changes in reward circuitry in response to intake of such foods serve a causal role in the development and maintenance of some cases of obesity. Finally, we discuss the potential value for future studies at the intersection of the obesity epidemic and the neuroscience of motivation, as well as the potential concerns that arise from viewing excessive food intake as an "addiction". We suggest that it might be more useful to focus on overeating that results in frank obesity, and multiple health, interpersonal, and occupational negative consequences as a form of food "abuse".
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Affiliation(s)
- Eric Stice
- Oregon Research Institute, 1776 Millrace Drive, Eugene, OR 97403, United States.
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Abstract
Anti-dieting sentiment has grown in recent years. Critics of restrained eating suggest that it evokes counter-regulatory responses that render it ineffective or even iatrogenic. However, restrained eaters are not in negative energy balance and overweight individuals show reduced eating problems when losing weight by dieting. A distinction is often drawn between physiological and psychological hunger, and neuroscience research has shown that there is a neurophysiological reality underlying this distinction. The brain has a homeostatic system (activated by energy deficits) and a hedonic system (activated by the presence of palatable food). The omnipresence of highly palatable food in the environment may chronically activate the hedonic appetite system, producing a need to actively restrain eating not just to lose weight but to avoid gaining it. Just as restricting energy intake below homeostatic needs produces physiological deprivation, restricting intake of palatable foods may produce "perceived deprivation" despite a state of energy balance. In summary, the motivation to eat more than one needs appears to be every bit as real, and perhaps every bit as powerful, as the motivation to eat when energy deprived.
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Affiliation(s)
- Michael R Lowe
- Department of Psychology, Drexel University, Mail Stop 626, 245 North Fifteenth Street, Philadelphia, PA 19102, USA.
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Alsiö J, Olszewski PK, Levine AS, Schiöth HB. Feed-forward mechanisms: addiction-like behavioral and molecular adaptations in overeating. Front Neuroendocrinol 2012; 33:127-39. [PMID: 22305720 DOI: 10.1016/j.yfrne.2012.01.002] [Citation(s) in RCA: 60] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/21/2011] [Revised: 11/24/2011] [Accepted: 01/13/2012] [Indexed: 12/23/2022]
Abstract
Food reward, not hunger, is the main driving force behind eating in the modern obesogenic environment. Palatable foods, generally calorie-dense and rich in sugar/fat, are thus readily overconsumed despite the resulting health consequences. Important advances have been made to explain mechanisms underlying excessive consumption as an immediate response to presentation of rewarding tastants. However, our understanding of long-term neural adaptations to food reward that oftentimes persist during even a prolonged absence of palatable food and contribute to the reinstatement of compulsive overeating of high-fat high-sugar diets, is much more limited. Here we discuss the evidence from animal and human studies for neural and molecular adaptations in both homeostatic and non-homeostatic appetite regulation that may underlie the formation of a "feed-forward" system, sensitive to palatable food and propelling the individual from a basic preference for palatable diets to food craving and compulsive, addiction-like eating behavior.
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Affiliation(s)
- Johan Alsiö
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Biomedical Center, Box 593, SE-751 24 Uppsala, Sweden.
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30
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Olszewski PK, Rozman J, Jacobsson JA, Rathkolb B, Strömberg S, Hans W, Klockars A, Alsiö J, Risérus U, Becker L, Hölter SM, Elvert R, Ehrhardt N, Gailus-Durner V, Fuchs H, Fredriksson R, Wolf E, Klopstock T, Wurst W, Levine AS, Marcus C, Hrabě de Angelis M, Klingenspor M, Schiöth HB, Kilimann MW. Neurobeachin, a regulator of synaptic protein targeting, is associated with body fat mass and feeding behavior in mice and body-mass index in humans. PLoS Genet 2012; 8:e1002568. [PMID: 22438821 PMCID: PMC3305408 DOI: 10.1371/journal.pgen.1002568] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2011] [Accepted: 01/16/2012] [Indexed: 01/08/2023] Open
Abstract
Neurobeachin (Nbea) regulates neuronal membrane protein trafficking and is required for the development and functioning of central and neuromuscular synapses. In homozygous knockout (KO) mice, Nbea deficiency causes perinatal death. Here, we report that heterozygous KO mice haploinsufficient for Nbea have higher body weight due to increased adipose tissue mass. In several feeding paradigms, heterozygous KO mice consumed more food than wild-type (WT) controls, and this consumption was primarily driven by calories rather than palatability. Expression analysis of feeding-related genes in the hypothalamus and brainstem with real-time PCR showed differential expression of a subset of neuropeptide or neuropeptide receptor mRNAs between WT and Nbea+/− mice in the sated state and in response to food deprivation, but not to feeding reward. In humans, we identified two intronic NBEA single-nucleotide polymorphisms (SNPs) that are significantly associated with body-mass index (BMI) in adult and juvenile cohorts. Overall, data obtained in mice and humans suggest that variation of Nbea abundance or activity critically affects body weight, presumably by influencing the activity of feeding-related neural circuits. Our study emphasizes the importance of neural mechanisms in body weight control and points out NBEA as a potential risk gene in human obesity. Body weight and energy balance are under very complex neural, endocrine, and metabolic control. Correspondingly, recent research suggests that hundreds of genes contribute to human obesity and that only a small proportion of them have as yet been identified. Neurobeachin (Nbea) is a protein specifically expressed in nerve and endocrine cells and is important for neurotransmission, apparently by influencing the synaptic targeting of membrane proteins. Here, we show that heterozygous knockout mice, expressing Nbea at 50% of normal levels, display increased adipose tissue mass, abnormal feeding behavior, and modified expression of specific genes in the brainstem and hypothalamus known to be important for body weight control. Moreover, we find that NBEA gene polymorphisms are associated with body-mass index in adult and juvenile human cohorts. Our results demonstrate that variation of Nbea activity critically affects body weight, presumably by influencing the activity of feeding-related neural circuits. They emphasize the importance of neural mechanisms in body weight control, and they identify NBEA as a potential genetic risk factor in human obesity.
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Affiliation(s)
- Pawel K. Olszewski
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
- Minnesota Obesity Center, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Jan Rozman
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Molecular Nutritional Medicine, Else Kröner-Fresenius Center and ZIEL Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Josefin A. Jacobsson
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Birgit Rathkolb
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Chair for Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-Universität München, München, Germany
| | - Siv Strömberg
- Molecular Cell Biology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Wolfgang Hans
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Anica Klockars
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Johan Alsiö
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Ulf Risérus
- Department of Public Health and Caring Sciences, Uppsala University, Uppsala, Sweden
| | - Lore Becker
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Department of Neurology, Friedrich-Baur-Institut, Ludwig-Maximilians-Universität München, München, Germany
| | - Sabine M. Hölter
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Developmental Genetics, Neuherberg, Germany
| | - Ralf Elvert
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Nicole Ehrhardt
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Valérie Gailus-Durner
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Helmut Fuchs
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
| | - Robert Fredriksson
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Eckhard Wolf
- Chair for Molecular Animal Breeding and Biotechnology, Gene Center, Ludwig-Maximilians-Universität München, München, Germany
| | - Thomas Klopstock
- Department of Neurology, Friedrich-Baur-Institut, Ludwig-Maximilians-Universität München, München, Germany
| | - Wolfgang Wurst
- Helmholtz Zentrum München, German Research Center for Environmental Health, Institute of Developmental Genetics, Neuherberg, Germany
- Max-Planck-Institute for Psychiatry, München, Germany
- Technical University München-Weihenstephan, Lehrstuhl für Entwicklungsgenetik c/o Helmholtz Zentrum München, Neuherberg, Germany
- Deutsches Zentrum für Neurodegenerative Erkrankungen (DZNE) Munich, Germany
| | - Allen S. Levine
- Minnesota Obesity Center, University of Minnesota, St. Paul, Minnesota, United States of America
| | - Claude Marcus
- Department for Clinical Science, Intervention, and Technology, Karolinska Institutet, Division of Pediatrics, National Childhood Obesity Centre, Stockholm, Sweden
| | - Martin Hrabě de Angelis
- German Mouse Clinic, Institute of Experimental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Neuherberg, Germany
- Lehrstuhl für Experimentelle Genetik, Technische Universität München, Freising-Weihenstephan, Germany
| | - Martin Klingenspor
- Molecular Nutritional Medicine, Else Kröner-Fresenius Center and ZIEL Research Center for Nutrition and Food Sciences, Technische Universität München, Freising-Weihenstephan, Germany
| | - Helgi B. Schiöth
- Functional Pharmacology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
| | - Manfred W. Kilimann
- Molecular Cell Biology Unit, Department of Neuroscience, Uppsala University, Uppsala, Sweden
- * E-mail:
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Rask-Andersen M, Almén MS, Olausen HR, Olszewski PK, Eriksson J, Chavan RA, Levine AS, Fredriksson R, Schiöth HB. Functional coupling analysis suggests link between the obesity gene FTO and the BDNF-NTRK2 signaling pathway. BMC Neurosci 2011; 12:117. [PMID: 22087873 PMCID: PMC3248879 DOI: 10.1186/1471-2202-12-117] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2010] [Accepted: 11/16/2011] [Indexed: 11/24/2022] Open
Abstract
Background The Fat mass and obesity gene (FTO) has been identified through genome wide association studies as an important genetic factor contributing to a higher body mass index (BMI). However, the molecular context in which this effect is mediated has yet to be determined. We investigated the potential molecular network for FTO by analyzing co-expression and protein-protein interaction databases, Coxpresdb and IntAct, as well as the functional coupling predicting multi-source database, FunCoup. Hypothalamic expression of FTO-linked genes defined with this bioinformatics approach was subsequently studied using quantitative real time-PCR in mouse feeding models known to affect FTO expression. Results We identified several candidate genes for functional coupling to FTO through database studies and selected nine for further study in animal models. We observed hypothalamic expression of Profilin 2 (Pfn2), cAMP-dependent protein kinase catalytic subunit beta (Prkacb), Brain derived neurotrophic factor (Bdnf), neurotrophic tyrosine kinase, receptor, type 2 (Ntrk2), Signal transducer and activator of transcription 3 (Stat3), and Btbd12 to be co-regulated in concert with Fto. Pfn2 and Prkacb have previously not been linked to feeding regulation. Conclusions Gene expression studies validate several candidates generated through database studies of possible FTO-interactors. We speculate about a wider functional role for FTO in the context of current and recent findings, such as in extracellular ligand-induced neuronal plasticity via NTRK2/BDNF, possibly via interaction with the transcription factor CCAAT/enhancer binding protein β (C/EBPβ).
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Affiliation(s)
- Mathias Rask-Andersen
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
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Mitra A, Kotz CM, Kim EM, Grace MK, Kuskowski MA, Billington CJ, Levine AS. Effects of butorphanol on feeding and neuropeptide Y in the rat. Pharmacol Biochem Behav 2011; 100:575-80. [PMID: 21925202 DOI: 10.1016/j.pbb.2011.08.010] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/05/2011] [Revised: 08/01/2011] [Accepted: 08/11/2011] [Indexed: 10/17/2022]
Abstract
Butorphanol ([BT] an opioid receptor agonist/antagonist) is different from other opioid agonists in that a single dose of BT can elicit up to 12 g of chow intake in a satiated rat whereas most opioid agonists induce a mild feeding response (2-3 g). Here, we first examined whether the effectiveness of BT to elicit feeding was affected by dose, method of infusion and possible tachyphylaxis following administration. Secondly, we examined whether BT administration influenced hypothalamic NPY gene expression and peptide levels. A single dose administration of BT (4 mg/kg) significantly increased food intake at 2, 3 and 6 h after administration. However following repeated injections of BT at 4 mg/kg, the cumulative long-term intake of BT-treated rats did not differ from that of controls, indicating that the animals compensate for the increased feeding following BT injection by decreased feeding at a later time. An ascending dose schedule of repeated BT injections resulted in additional feeding. NPY gene expression in the ARC was influenced by how much food had been consumed, but not by BT. The amount of food consumed and the level of NPY mRNA were inversely correlated. This is consistent with NPY's role in normal feeding. BT treatment did not affect either NPY or leptin RIA levels. We conclude that the feeding produced by BT is sensitive to dose and dosing paradigm. Further, its mechanism of action does not appear to be mediated by NPY or leptin pathways.
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Affiliation(s)
- A Mitra
- University of Minnesota, Minneapolis, MN, USA
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Mitra A, Klockars A, Gosnell BA, Le Grevès M, Olszewski PK, Levine AS, Schiöth HB. Expression levels of genes encoding melanin concentrating hormone (MCH) and MCH receptor change in taste aversion, but MCH injections do not alleviate aversive responses. Pharmacol Biochem Behav 2011; 100:581-6. [PMID: 21925200 DOI: 10.1016/j.pbb.2011.08.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/06/2011] [Revised: 08/01/2011] [Accepted: 08/11/2011] [Indexed: 12/24/2022]
Abstract
Melanin concentrating hormone (MCH) stimulates feeding driven by energy needs and reward and modifies anxiety behavior. Orexigenic peptides of similar characteristics, including nociceptin/orphanin FQ, Agouti-related protein and opioids, increase consumption also by reducing avoidance of potentially tainted food in animals displaying a conditioned taste aversion (CTA). Herein, using real-time PCR, we assessed whether expression levels of genes encoding MCH and its receptor, MCHR1, were affected in CTA in the rat. We also investigated whether injecting MCH intracerebroventricularly (ICV) during the acquisition and retrieval of LiCl-induced CTA, would alleviate aversive responses. MCHR1 gene was upregulated in the hypothalamus and brain stem of aversive animals, MCH mRNA was significantly higher in the hypothalamus, whereas a strong trend suggesting upregulation of MCH and MCHR1 genes was detected in the amygdala. Despite these expression changes associated with aversion, MCH injected prior to the induction of CTA with LiCl as well as later, during the CTA retrieval upon subsequent presentations of the aversive tastant, did not reduce the magnitude of CTA. We conclude that MCH and its receptor form an orexigenic system whose expression is affected in CTA. This altered MCH expression may contribute to tastant-targeted hypophagia in CTA. However, changing the MCH tone in the brain by exogenous peptide was insufficient to prevent the onset or facilitate extinction of LiCl-induced CTA. This designates MCH as one of many accessory molecules associated with shaping an aversive response, but not a critical one for LiCl-dependent CTA to occur.
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Affiliation(s)
- Anaya Mitra
- Department of Food Science and Nutrition, University of Minnesota, Saint Paul, MN, USA.
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Cedernaes J, Olszewski PK, Almén MS, Stephansson O, Levine AS, Fredriksson R, Nylander O, Schiöth HB. Comprehensive analysis of localization of 78 solute carrier genes throughout the subsections of the rat gastrointestinal tract. Biochem Biophys Res Commun 2011; 411:702-7. [DOI: 10.1016/j.bbrc.2011.07.005] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2011] [Accepted: 07/02/2011] [Indexed: 01/07/2023]
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Olszewski PK, Fredriksson R, Eriksson JD, Mitra A, Radomska KJ, Gosnell BA, Solvang MN, Levine AS, Schiöth HB. Fto colocalizes with a satiety mediator oxytocin in the brain and upregulates oxytocin gene expression. Biochem Biophys Res Commun 2011; 408:422-6. [PMID: 21514276 DOI: 10.1016/j.bbrc.2011.04.037] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2011] [Accepted: 04/07/2011] [Indexed: 12/31/2022]
Abstract
Single nucleotide polymorphisms in the fat mass and obesity-associated (FTO) gene have been associated with obesity in humans. Alterations in Fto expression in transgenic animals affect body weight, energy expenditure and food intake. Fto, a nuclear protein and proposed transcription co-factor, has been speculated to affect energy balance through a functional relationship with specific genes encoding feeding-related peptides. Herein, we employed double immunohistochemistry and showed that the majority of neurons synthesizing a satiety mediator, oxytocin, coexpress Fto in the brain of male and female mice. We then overexpressed Fto in a murine hypothalamic cell line and, using qPCR, detected a 50% increase in the level of oxytocin mRNA. Expression levels of several other feeding-related genes, including neuropeptide Y (NPY) and Agouti-related protein (AgRP), were unaffected by the FTO transfection. Addition of 10 and 100 nmol oxytocin to the cell culture medium did not affect Fto expression in hypothalamic cells. We conclude that Fto, a proposed transcription co-factor, influences expression of the gene encoding a satiety mediator, oxytocin.
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Affiliation(s)
- Pawel K Olszewski
- Department of Neuroscience, Functional Pharmacology, Uppsala University, 75124 Uppsala, Sweden.
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Olszewski PK, Radomska KJ, Ghimire K, Klockars A, Ingman C, Olszewska AM, Fredriksson R, Levine AS, Schiöth HB. Fto immunoreactivity is widespread in the rodent brain and abundant in feeding-related sites, but the number of Fto-positive cells is not affected by changes in energy balance. Physiol Behav 2011; 103:248-53. [PMID: 21295049 DOI: 10.1016/j.physbeh.2011.01.022] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2010] [Revised: 01/14/2011] [Accepted: 01/24/2011] [Indexed: 10/18/2022]
Abstract
A single nucleotide polymorphism in the FTO gene is associated with obesity in humans. Evidence gathered in animals mainly relates energy homeostasis to the central FTO mRNA levels, but our knowledge of the Fto protein distribution and regulation is limited. Fto, a demethylase and transcriptional coactivator, is thought to regulate expression of other genes. Herein, we examined Fto immunoreactivity (IR) in the mouse and rat brain with emphasis on sites governing energy balance. We also studied whether energy status affects central Fto IR. We report that Fto IR, limited to nuclear profiles, is widespread in the brain, in- and outside feeding circuits; it shows a very similar distribution in feeding-related sites in mice and rats. Several areas regulating energy homeostasis display enhanced intensity of Fto staining: the arcuate, paraventricular, supraoptic, dorsomedial, ventromedial nuclei, and dorsal vagal complex. Some regions mediating feeding reward, including the bed nucleus of the stria terminalis, have ample Fto IR. We found that differences in energy status between rats fed ad libitum, deprived or refed following deprivation, did not affect the number of Fto-positive nuclei in 10 sites governing consumption for energy or reward. We conclude that Fto IR, widespread in the rodent brain, is particularly abundant in feeding circuits, but the number of Fto-positive neurons is unaffected by changes in energy balance.
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Affiliation(s)
- Pawel K Olszewski
- Department of Neuroscience, Functional Pharmacology, Uppsala University, 75124 Uppsala, Sweden.
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Olszewski PK, Klockars A, Olszewska AM, Fredriksson R, Schiöth HB, Levine AS. Molecular, immunohistochemical, and pharmacological evidence of oxytocin's role as inhibitor of carbohydrate but not fat intake. Endocrinology 2010; 151:4736-44. [PMID: 20685878 PMCID: PMC2946140 DOI: 10.1210/en.2010-0151] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
Oxytocin (OT) facilitates feeding termination stemming from high osmolality, stomach distention, and malaise. Recent knockout (KO) studies suggested a crucial function for OT in carbohydrate intake: OT-/- mice had increased preference for carbohydrates, including sucrose, but not fat (Intralipid). In striking contrast, sugar appetite was unaffected in the OT receptor KO mouse; data from wild-type animals have been insufficient. Therefore, we examined the involvement of OT in the regulation of sucrose vs. fat intake in C57BL/6 mice that served as a background KO strain. We exposed mice to a meal of sucrose or Intralipid and determined that the percentage of c-Fos-immunoreactive paraventricular hypothalamic OT neurons was elevated at termination of intake of either of the tastants, but this increase was 2-fold higher in sucrose-fed mice. A 48-h exposure to sucrose compared with Intralipid caused up-regulation of OT mRNA, whereas inherent individual preferences for sucrose vs. fat were not associated with differences in baseline OT expression as established with quantitative PCR. We found that L-368,899, an OT receptor antagonist, increased sugar intake when sucrose was presented alone or concurrently with Intralipid; it had no effect on Intralipid or total calorie consumption. L-368,899 affected Fos immunoreactivity in the paraventricular hypothalamus, arcuate nucleus, amygdala, and nucleus of the solitary tract, areas involved in aversion, satiety, and reward. This pattern serves as neuroanatomical basis of OT's complex role in food intake, including sucrose intake. The current findings expand our knowledge on OT and suggest that it acts as a carbohydrate-specific inhibitor of feeding.
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Affiliation(s)
- Pawel K Olszewski
- Minnesota Obesity Center, University of Minnesota, Department of Food Science and Nutrition, 1334 Eckles Avenue, Saint Paul, Minnesota 55108, USA
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Olszewski PK, Grace MK, Fard SS, Le Grevès M, Klockars A, Massi M, Schiöth HB, Levine AS. Central nociceptin/orphanin FQ system elevates food consumption by both increasing energy intake and reducing aversive responsiveness. Am J Physiol Regul Integr Comp Physiol 2010; 299:R655-63. [PMID: 20427724 PMCID: PMC3774471 DOI: 10.1152/ajpregu.00556.2009] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2009] [Accepted: 04/23/2010] [Indexed: 11/22/2022]
Abstract
Nociceptin/orphanin FQ (N/OFQ), the nociceptin opioid peptide (NOP) receptor ligand, increases feeding when injected centrally. Initial data suggest that N/OFQ blocks the development of a conditioned taste aversion (CTA). The current project further characterized the involvement of N/OFQ in the regulation of hunger vs. aversive responses in rats by employing behavioral, immunohistochemical, and real-time PCR methodology. We determined that the same low dose of the NOP antagonist [Nphe(1)]N/OFQ(1-13)NH(2) delivered via the lateral ventricle diminishes both N/OFQ- and deprivation-induced feeding. This anorexigenic effect did not stem from aversive consequences, as the antagonist did not cause the development of a CTA. When [Nphe(1)]N/OFQ(1-13)NH(2) was administered with LiCl, it moderately delayed extinction of the LiCl-induced CTA. Injection of LiCl + antagonist compared with LiCl alone generated an increase in c-Fos immunoreactivity in the central nucleus of the amygdala. The antagonist alone elevated Fos immunoreactivity in the paraventricular nucleus of the hypothalamus, nucleus of the solitary tract, and central nucleus of the amygdala. Hypothalamic NOP mRNA levels were decreased during energy intake restriction induced by aversion, as well as in non-CTA rats food-restricted to match CTA-reduced consumption. Brain stem NOP was upregulated only in aversion. Prepro-N/OFQ mRNA showed a trend toward upregulation in restricted rats (P = 0.068). We conclude that the N/OFQ system promotes feeding by affecting the need to replenish lacking calories and by reducing aversive responsiveness. It may belong to mechanisms that shift a balance between the drive to ingest energy and avoidance of potentially tainted food.
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Mitra A, Gosnell BA, Schiöth HB, Grace MK, Klockars A, Olszewski PK, Levine AS. Chronic sugar intake dampens feeding-related activity of neurons synthesizing a satiety mediator, oxytocin. Peptides 2010; 31:1346-52. [PMID: 20399242 PMCID: PMC3175817 DOI: 10.1016/j.peptides.2010.04.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/01/2010] [Revised: 04/06/2010] [Accepted: 04/07/2010] [Indexed: 01/08/2023]
Abstract
Increased tone of orexigens mediating reward occurs upon repeated consumption of sweet foods. Interestingly, some of these reward orexigens, such as opioids, diminish activity of neurons synthesizing oxytocin, a nonapeptide that promotes satiety and feeding termination. It is not known, however, whether consumption-related activity of the central oxytocin system is modified under chronic sugar feeding reward itself. Therefore, we examined how chronic consumption of a rewarding high-sucrose (HS) vs. bland cornstarch (CS) diet affected the activity of oxytocin cells in the hypothalamus at the time of meal termination. Schedule-fed (2h/day) rats received either a HS or CS powdered diet for 20 days. On the 21st day, they were given the same or the opposite diet, and food was removed after the main consummatory activity was completed. Animals were perfused 60 min after feeding termination and brains were immunostained for oxytocin and the marker of neuronal activity, c-Fos. The percentage of c-Fos-positive oxytocin cells in the hypothalamic paraventricular nucleus was significantly lower in rats chronically exposed to the HS than to the CS diet, regardless of which diet they received on the final day. A similar pattern was observed in the supraoptic nucleus. We conclude that the chronic rather than acute sucrose intake reduces activity of the anorexigenic oxytocin system. These findings indicate that chronic consumption of sugar blunts activity of pathways that mediate satiety. We speculate that a reduction in central satiety signaling precipitated by regular intake of foods high in sugar may lead to generalized overeating.
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Affiliation(s)
- Anaya Mitra
- Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave., St. Paul, MN 55108, USA.
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Wang C, Bomberg E, Billington CJ, Levine AS, Kotz CM. Brain-derived neurotrophic factor (BDNF) in the hypothalamic ventromedial nucleus increases energy expenditure. Brain Res 2010; 1336:66-77. [PMID: 20398635 PMCID: PMC4452019 DOI: 10.1016/j.brainres.2010.04.013] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2010] [Revised: 03/30/2010] [Accepted: 04/02/2010] [Indexed: 10/19/2022]
Abstract
Brain-derived neurotrophic factor (BDNF) decreases food intake and body weight, but few central sites of action have been identified for its effect on energy expenditure. The hypothalamic ventromedial nucleus (VMH) is important in regulating energy metabolism. Our previous work indicated that BDNF in the VMH reduced food intake. The purposes of the study were to determine: 1) if BDNF in the VMH increases energy expenditure (EE); 2) if BDNF-enhanced thermogenesis results from increased spontaneous physical activity (SPA) and resting metabolic rate (RMR); and 3) if VMH BDNF thermogenic effects are mediated by uncoupling protein 1 (UCP1) in brown adipose tissue (BAT). BDNF (0.5 microg) was injected into the VMH of male Sprague-Dawley rats and oxygen consumption, carbon dioxide production, food intake and SPA were measured for 24h in an indirect calorimeter. Animals were sacrificed 4h after BDNF injection, and BAT UCP1 gene expression was measured with quantitative real-time polymerase chain reaction. BDNF significantly decreased food and water intake, and body weight gain. Heat production and RMR were significantly elevated for 9h immediately after BDNF injection. BDNF increased SPA and EE during SPA (aEE) within 9h after injection although BDNF had no effect on 0-24h SPA and aEE. BDNF did not induce a significant increase in BAT UCP1 expression. In conclusion, VMH BDNF reduces body weight by decreasing food intake and increasing EE consequent to increased SPA and RMR, suggesting that the VMH is an important site of BDNF action to influence energy balance.
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Affiliation(s)
- Chuanfeng Wang
- Veterans Affairs Medical Center, Minneapolis, MN 55417, USA.
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Olszewski PK, Klockars A, Schiöth HB, Levine AS. Oxytocin as feeding inhibitor: maintaining homeostasis in consummatory behavior. Pharmacol Biochem Behav 2010; 97:47-54. [PMID: 20595062 DOI: 10.1016/j.pbb.2010.05.026] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/15/2010] [Revised: 05/12/2010] [Accepted: 05/26/2010] [Indexed: 12/13/2022]
Abstract
Initial studies showed that the anorexigenic peptide oxytocin (OT) regulates gastric motility, responds to stomach distention and to elevated osmolality, and blocks consumption of toxic foods. Most recently, it has been proposed to act as a mediator of general and carbohydrate-specific satiety and regulator of body weight. In the current review, we discuss the function of OT as a homeostatic inhibitor of consumption, capable of mitigating multiple aspects of ingestive behavior and energy metabolism.
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Affiliation(s)
- Pawel K Olszewski
- Minnesota Obesity Center, Department of Food Science and Nutrition, University of Minnesota, St. Paul, MN 55108, USA
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Almén MS, Jacobsson JA, Shaik JHA, Olszewski PK, Cedernaes J, Alsiö J, Sreedharan S, Levine AS, Fredriksson R, Marcus C, Schiöth HB. The obesity gene, TMEM18, is of ancient origin, found in majority of neuronal cells in all major brain regions and associated with obesity in severely obese children. BMC Med Genet 2010; 11:58. [PMID: 20380707 PMCID: PMC2858727 DOI: 10.1186/1471-2350-11-58] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/24/2009] [Accepted: 04/09/2010] [Indexed: 11/10/2022]
Abstract
BACKGROUND TMEM18 is a hypothalamic gene that has recently been linked to obesity and BMI in genome wide association studies. However, the functional properties of TMEM18 are obscure. METHODS The evolutionary history of TMEM18 was inferred using phylogenetic and bioinformatic methods. The gene's expression profile was investigated with real-time PCR in a panel of rat and mouse tissues and with immunohistochemistry in the mouse brain. Also, gene expression changes were analyzed in three feeding-related mouse models: food deprivation, reward and diet-induced increase in body weight. Finally, we genotyped 502 severely obese and 527 healthy Swedish children for two SNPs near TMEM18 (rs6548238 and rs756131). RESULTS TMEM18 was found to be remarkably conserved and present in species that diverged from the human lineage over 1500 million years ago. The TMEM18 gene was widely expressed and detected in the majority of cells in all major brain regions, but was more abundant in neurons than other cell types. We found no significant changes in the hypothalamic and brainstem expression in the feeding-related mouse models. There was a strong association for two SNPs (rs6548238 and rs756131) of the TMEM18 locus with an increased risk for obesity (p = 0.001 and p = 0.002). CONCLUSION We conclude that TMEM18 is involved in both adult and childhood obesity. It is one of the most conserved human obesity genes and it is found in the majority of all brain sites, including the hypothalamus and the brain stem, but it is not regulated in these regions in classical energy homeostatic models.
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Affiliation(s)
- Markus Sällman Almén
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Josefin A Jacobsson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Jafar HA Shaik
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Pawel K Olszewski
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
| | - Jonathan Cedernaes
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Johan Alsiö
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Smitha Sreedharan
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Allen S Levine
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
- Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Claude Marcus
- Department for Clinical Science, Intervention and Technology, Karolinska Institutet, Division of Pediatrics, National Childhood Obesity Centre, Stockholm, Sweden
| | - Helgi B Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
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Gosnell BA, Mitra A, Avant RA, Anker JJ, Carroll ME, Levine AS. Operant responding for sucrose by rats bred for high or low saccharin consumption. Physiol Behav 2010; 99:529-33. [PMID: 20096717 DOI: 10.1016/j.physbeh.2010.01.010] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2009] [Revised: 12/21/2009] [Accepted: 01/11/2010] [Indexed: 11/28/2022]
Abstract
The use of rats differing in the intake of sweet substances has highlighted some interesting parallels between taste preferences and drug self-administration. For example, rats selectively bred to consume high (HiS) or low (LoS) amounts of a 0.1% saccharin solution (when compared to water consumption), show corresponding differences across several measures of cocaine self-administration (HiS>LoS). In this study, we measured whether the two strains also differ when response requirements are imposed for obtaining a sucrose reinforcer. Male HiS and LoS rats were measured for operant responding for sucrose pellets under fixed-ratio (FR) schedules of 1, 3, 5 and 10 and under a progressive-ratio (PR) schedule, during which the response requirement for each successive pellet increased exponentially. The effect of systemic naltrexone (0.3, 1 and 3mg/kg) on PR responding for sucrose pellets was also tested. Under all FR and PR schedules, the number of pellets obtained by the LoS rats were significantly lower than those obtained by the HiS rats. Although the LoS weighed more than the HiS rats, this difference does not appear to explain differences in operant behavior. No strain differences in the effect of naltrexone were observed; the 3mg/kg dose reduced the number of pellets obtained in both strains. Measures of locomotor activity taken prior to operant trials suggest that the differences in responding were not due to differences in general activity levels. These studies provide further characterization of the HiS and LoS rat lines by demonstrating that motivation to consume sucrose is greater in HiS than in LoS rats.
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Affiliation(s)
- Blake A Gosnell
- Department of Food Science and Nutrition, University of Minnesota, 1334 Eckles Ave., St. Paul, MN 55108, USA.
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Sreedharan S, Shaik JHA, Olszewski PK, Levine AS, Schiöth HB, Fredriksson R. Glutamate, aspartate and nucleotide transporters in the SLC17 family form four main phylogenetic clusters: evolution and tissue expression. BMC Genomics 2010; 11:17. [PMID: 20059771 PMCID: PMC2824716 DOI: 10.1186/1471-2164-11-17] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Accepted: 01/08/2010] [Indexed: 11/12/2022] Open
Abstract
Background The SLC17 family of transporters transports the amino acids: glutamate and aspartate, and, as shown recently, also nucleotides. Vesicular glutamate transporters are found in distinct species, such as C. elegans, but the evolutionary origin of most of the genes in this family has been obscure. Results Our phylogenetic analysis shows that the SLC17 family consists of four main phylogenetic clades which were all present before the divergence of the insect lineage. One of these clades has not been previously described and it is not found in vertebrates. The clade containing Slc17a9 had the most restricted evolutionary history with only one member in most species. We detected expression of Slc17a1-17a4 only in the peripheral tissues but not in the CNS, while Slc17a5- Slc17a9 are highly expressed in both the CNS and periphery. Conclusions The in situ hybridization studies on vesicular nucleotide transporter revealed high expression throughout the cerebral cortex, certain areas in the hippocampus and in specific nuclei of the hypothalamus and thalamus. Some of the regions with high expression, such as the medial habenula and the dentate gyrus of the hippocampus, are important sites for purinergic neurotransmission. Noteworthy, other areas relying on purine-mediated signaling, such as the molecular layer of the dentate gyrus and the periaqueductal gray, lack or have a very low expression of Slc17a9, suggesting that there could be another nucleotide transporter in these regions.
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Affiliation(s)
- Smitha Sreedharan
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
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Olszewski PK, Fredriksson R, Olszewska AM, Stephansson O, Alsiö J, Radomska KJ, Levine AS, Schiöth HB. Hypothalamic FTO is associated with the regulation of energy intake not feeding reward. BMC Neurosci 2009; 10:129. [PMID: 19860904 PMCID: PMC2774323 DOI: 10.1186/1471-2202-10-129] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/23/2009] [Accepted: 10/27/2009] [Indexed: 11/10/2022] Open
Abstract
Background Polymorphism in the FTO gene is strongly associated with obesity, but little is known about the molecular bases of this relationship. We investigated whether hypothalamic FTO is involved in energy-dependent overconsumption of food. We determined FTO mRNA levels in rodent models of short- and long-term intake of palatable fat or sugar, deprivation, diet-induced increase in body weight, baseline preference for fat versus sugar as well as in same-weight animals differing in the inherent propensity to eat calories especially upon availability of diverse diets, using quantitative PCR. FTO gene expression was also studied in organotypic hypothalamic cultures treated with anorexigenic amino acid, leucine. In situ hybridization (ISH) was utilized to study FTO signal in reward- and hunger-related sites, colocalization with anorexigenic oxytocin, and c-Fos immunoreactivity in FTO cells at initiation and termination of a meal. Results Deprivation upregulated FTO mRNA, while leucine downregulated it. Consumption of palatable diets or macronutrient preference did not affect FTO expression. However, the propensity to ingest more energy without an effect on body weight was associated with lower FTO mRNA levels. We found that 4-fold higher number of FTO cells displayed c-Fos at meal termination as compared to initiation in the paraventricular and arcuate nuclei of re-fed mice. Moreover, ISH showed that FTO is present mainly in hunger-related sites and it shows a high degree of colocalization with anorexigenic oxytocin. Conclusion We conclude that FTO mRNA is present mainly in sites related to hunger/satiation control; changes in hypothalamic FTO expression are associated with cues related to energy intake rather than feeding reward. In line with that, neurons involved in feeding termination express FTO. Interestingly, baseline FTO expression appears linked not only with energy intake but also energy metabolism.
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Affiliation(s)
- Pawel K Olszewski
- Department of Neuroscience, Functional Pharmacology, Uppsala University, Uppsala, Sweden.
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Clancy K, Hamm M, Levine AS, Wilkins J. Organics: Evidence of Health Benefits Lacking. Science 2009; 325:676. [DOI: 10.1126/science.325_676a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Affiliation(s)
- Kate Clancy
- Minnesota Institute for Sustainable Agriculture, University of Minnesota, St. Paul, MN 55108–6074, USA
| | - Michael Hamm
- Community, Agriculture, Recreation, and Resources, Michigan State University, East Lansing, MI 48824–1222, USA
| | - Allen S. Levine
- College of Food, Agricultural, and Natural Resource Sciences, University of Minnesota, St. Paul, MN 55108–6074, USA
| | - Jennifer Wilkins
- Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853–4401, USA
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Affiliation(s)
- Allen S. Levine
- College of Food, Agricultural, and Natural Resource Sciences, University of Minnesota, St. Paul, MN 55108–6074, USA, and Minnesota Obesity Center, Minneapolis VA Medical Center, Minneapolis, MN 55417, USA
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Jewett DC, Hahn TW, Smith TR, Fiksdal BL, Wiebelhaus JM, Dunbar AR, Filtz CR, Novinska NL, Levine AS. Effects of sibutramine and rimonabant in rats trained to discriminate between 22- and 2-h food deprivation. Psychopharmacology (Berl) 2009; 203:453-9. [PMID: 18854986 DOI: 10.1007/s00213-008-1350-1] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/02/2008] [Accepted: 09/20/2008] [Indexed: 11/24/2022]
Abstract
OBJECTIVE The objective of the study was to evaluate whether sibutramine and rimonabant, drugs that decrease food intake in human and non-human animals, affect the discriminative stimulus effects associated with acute food deprivation ("hunger"). MATERIALS AND METHODS Rats were trained to discriminate between 22- and 2-h food deprivation in a two-lever choice procedure. After rats acquired the discrimination, subjects were food-restricted for 22 h and administered with sibutramine (0.32-10 mg/kg, p.o.) or rimonabant (0.32-10 mg/kg, s.c.) before a generalization test session. RESULTS Sibutramine (3.2 mg/kg) produced significant decreases in 22-h deprivation-appropriate responding, response rates (resulting in lever pressing rates similar to those following 2-h food deprivation), and food intake measured 1 h after the generalization test. A larger sibutramine dose eliminated responding and significantly reduced food intake. Rimonabant did not alter the discriminative stimulus effects of 22-h food deprivation, but rimonabant did significantly reduce both response rates and food intake. CONCLUSION Sibutramine appears to decrease food intake by reducing hunger sensations associated with food deprivation. In contrast, rimonabant does not alter the discrimination of acute food deprivation. The use of food-deprivation discrimination techniques may be useful in identifying the role of specific neuroactive compounds in eating stimulated by a sense of hunger and may aid in medication development for more effective treatments for obesity and other eating-related conditions.
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Affiliation(s)
- David C Jewett
- Department of Psychology, University of Wisconsin-Eau Claire, Eau Claire, WI, USA.
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Olszewski PK, Shaw TJ, Grace MK, Höglund CE, Fredriksson R, Schiöth HB, Levine AS. Complexity of neural mechanisms underlying overconsumption of sugar in scheduled feeding: involvement of opioids, orexin, oxytocin and NPY. Peptides 2009; 30:226-33. [PMID: 19022308 PMCID: PMC2657876 DOI: 10.1016/j.peptides.2008.10.011] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/21/2008] [Revised: 10/19/2008] [Accepted: 10/20/2008] [Indexed: 11/23/2022]
Abstract
A regular daily meal regimen, as opposed to ad libitum consumption, enforces eating at a predefined time and within a short timeframe. Hence, it is important to study food intake regulation in animal feeding models that somewhat reflect this pattern. We investigated the effect of scheduled feeding on the intake of a palatable, high-sugar diet in rats and attempted to define central mechanisms - especially those related to opioid signaling--responsible for overeating sweet foods under such conditions. We found that scheduled access to food, even as challenging as 20 min per day, does not prevent overconsumption of a high-sucrose diet compared to a standard one. An opioid receptor antagonist, naloxone, at 0.3-1 mg/kg b. wt., decreased the intake of the sweet diet, whereas higher doses were required to reduce bland food consumption. Real-time PCR analysis revealed that expression of hypothalamic and brainstem genes encoding opioid peptides and receptors did not differ in sucrose versus regular diet-fed rats, which suggests that scheduled intake of sweet food produces only a transient change in the opioid tone. Intake of sugar was also associated with upregulation of orexin and oxytocin genes in the hypothalamus and NPY in the brainstem. We conclude that scheduled consumption of sugar diets is associated with activity of a complex network of neuroregulators involving opioids, orexin, oxytocin and NPY.
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Affiliation(s)
- Pawel K. Olszewski
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
| | - Timothy J. Shaw
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
- Bethel University, Arden Hills, MN 55112, USA
| | - Martha K. Grace
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
| | - Catherine E. Höglund
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Robert Fredriksson
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Helgi B. Schiöth
- Department of Neuroscience, Functional Pharmacology, Uppsala University, BMC, Uppsala SE 75124, Sweden
| | - Allen S. Levine
- Minnesota Obesity Center, Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
- Department of Food Science and Nutrition, Saint Paul, MN 55108, USA
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Beckman TR, Shi Q, Levine AS, Billington CJ. Amygdalar opioids modulate hypothalamic melanocortin-induced anorexia. Physiol Behav 2008; 96:568-73. [PMID: 19136019 DOI: 10.1016/j.physbeh.2008.12.007] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2008] [Revised: 11/18/2008] [Accepted: 12/10/2008] [Indexed: 11/17/2022]
Abstract
We wanted to assess the possibility that opioid activity in the central amygdala (CeA) could modulate the feeding inhibition of melanocortin stimulation of the paraventricular hypothalamus (PVN). The melanocortin system is important in both the acute regulation of satiety and feeding behavior and in the integration of long-term appetite signals. Melanotan II (MTII) is a synthetic MC3R and MC4R agonist which reduces food intake when given intracerebroventricularly (ICV) and into the PVN. Tyr-D-Ala-Gly-(me) Phe-Gly-ol (DAMGO), a micro-opioid receptor agonist, increases food intake, while opioid antagonists, like naltrexone (NTX), inhibit food intake after injection into many brain sites involved in appetite regulation, including the CeA. In food-deprived male Sprague-Dawley rats, co-injected intra-PVN MTII partially blocked the orexigenic effect of co-injected intra-CeA DAMGO. Intra-CeA NTX co-injected with intra-PVN MTII reduced food intake significantly more than either alone. NTX administered intra-CeA reduced c-Fos-immunoreactivity (IR) in nucleus accumbens neurons significantly compared to the intra-PVN MTII treated animals, animals co-injected intra-PVN with MTII and intra-CeA with NTX animals, and control animals. Intra-PVN MTII induced c-Fos-IR in significantly more PVN neurons than observed in control animals. Intra-CeA NTX co-injected with intra-PVN MTII induced c-Fos-IR significantly in PVN neurons relative to control and intra-CeA NTX animals. Such data support the significance of opioid action within the CeA as a modulator of the feeding regulation action of melanocortins within the PVN, occurring within the context of a larger appetitive network.
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MESH Headings
- Amygdala/drug effects
- Amygdala/metabolism
- Analgesics, Opioid/metabolism
- Animals
- Appetite Regulation/drug effects
- Appetite Regulation/physiology
- Drug Interactions
- Eating/drug effects
- Eating/physiology
- Enkephalin, Ala(2)-MePhe(4)-Gly(5)-/pharmacology
- Food Deprivation
- Hormones/pharmacology
- Male
- Melanocortins/metabolism
- Naltrexone/pharmacology
- Neural Pathways/physiology
- Neurotransmitter Agents/pharmacology
- Paraventricular Hypothalamic Nucleus/drug effects
- Paraventricular Hypothalamic Nucleus/metabolism
- Peptides, Cyclic/pharmacology
- Rats
- Rats, Sprague-Dawley
- Receptor, Melanocortin, Type 3/drug effects
- Receptor, Melanocortin, Type 3/metabolism
- Receptor, Melanocortin, Type 4/drug effects
- Receptor, Melanocortin, Type 4/metabolism
- Receptors, Opioid, mu/drug effects
- Receptors, Opioid, mu/metabolism
- alpha-MSH/analogs & derivatives
- alpha-MSH/pharmacology
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Affiliation(s)
- Tiffany R Beckman
- Department of Medicine, University of Minnesota, Minneapolis, MN 55455, United States.
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