Effects of palatable diets on appetite regulation, appetite peptides and neurogenesis.

Abstract

Obesity is increasing throughout the world at an epidemic rate, partly due to increased consumption of diets rich in fat and/or sugar. Ghrelin and leptin are hormones, originating from the periphery, involved in the regulation of food intake and of maintaining energy homeostasis. Circulating ghrelin levels increase in times of energy deficiency, such as fasting, signalling hunger whereas circulating leptin levels increase during food intake, signaling termination of feeding. In rats offered a diet rich in sucrose, the pre- and postprandial difference in circulating leptin and ghrelin was abolished. This difference in leptin was also abolished in rats offered a high fat diet. Circulating concentrations of leptin was increased whereas ghrelin concentrations were decreased in the fasted state of rats offered a diet rich in both fat and sucrose. This suggests that the animals are trying to defend themselves against, or ameliorate the effects of, the energy-dense diets. This attempt to protect themselves is, however, not efficient enough to prevent the rats from overconsumption of the diets and gaining weight. Interestingly, fructose, a form of sugar very commonly used as a sweetener in soft drinks and other sweetened beverages, was found to increase fasting levels of ghrelin, thus promoting increased caloric consumption.



The removal of the stomach (gastrectomy) in mice resulted in an 80% reduction in circulating ghrelin (hypoghrelinemia), in decreased amount of adipose tissue and decreased thermogenesis and ghrelin, when given daily over a period of eight weeks, normalised the amount of adipose tissue and thermogenesis in gastrectomised mice.



A high fat diet was offered to rats in order to study the effect of such a diet on hippocampal neurogenesis. The high fat diet was found to impair neurogenesis in male rats, as indicated by a 40% reduction in newborn neurons. This effect was not observed in female rats. The high fat diet was also found to stimulate corticosterone in male rats (but not female rats), suggesting corticosterone to be responsible for the impairment in hippocampal neurogenesis.

Abstract (Swedish)

Popular Abstract in Swedish

Fetma ökar epidemilikt i hela världen, delvis på grund av en ökad konsumption av dieter som innehåller mycket fett och/eller socker. Ghrelin och leptin är hormoner som produceras perifert med effekter på födointag och energihomeostas. Ghrelin i cirkulationen ökar vid energibrist, t ex vid fasta och signalerar därmed hunger. Leptin ökar vid födointag och signalerar mättnad. Råttor som fått en diet med mycket socker i hade ingen skillnad mellan faste och postprandiella nivåer av leptin och ghrelin. Denna skillnad försvann också i råttor som fått en fettrik diet att äta. Leptin- och ghrelinnivåerna var förhöjda hos råttor som fått äta en diet med både mycket fett och socker. Dessa förändringar i leptin och ghrelin ser vi som ett sätt för djuren att försöka försvara sig mot en överkonsumption av dessa kaloritäta dieter. Detta försök är dock inte effektivt nog utan djuren går upp mer i vikt än kontrolldjuren som fått en kalorisnål diet. Vi fann en intressant sak, nämligen att fruktos, som är ett vanligt sötningsmedel, ökade nivåerna av både leptin och ghrelin.



En gastrektomi, d v s avlägsnandet av magen, resulterar i en 80%-ig minskning av ghrelin i cirkulationen, minskade fettdepåer och en minskad termogenes. Daglig administration av ghrelin till gastrektomerade möss resulterade i en normalisering av fettmängden och termogenesen.



Råttor som ätit en fettrik diet under fyra veckor visade sig ha en försämrad neurogenes, d v s de hade ett mindre antal nyfödda nervceller, jämfört med kontrolldjuren som ätit fettsnål diet. De råttor som ätit en fettrik diet hade ökad nivåer av kortikosteron i cirkulatione jämfört med kontrolldjuren.

• author: Lindqvist, Andreas
• supervisor: Charlotte Erlanson-Albertsson
• opponent: Professor Blundell, John, Leeds University
• organization: Appetite Regulation (research group)
• publishing date: 2006
• type: Thesis
• publication status: published
• subject: Basic Medicine
• keywords: sekretion, Endokrinologi, diabetologi, Appetite regulation, Ghrelin, Obesity, Leptin, Endocrinology, diabetology, secreting systems
• defense location: Segerfalk Lecture Hall, BMC, Sölvegatan 19, Lund, Sweden
• defense date: 2006-12-01 09:15:00
• ISBN: 91-85559-60-1
• language: English
• LU publication?: yes
• additional info: Andreas Lindqvist, Charlotta Dornonville de la Cour, Anna Stegmark, Rolf Håkanson and Charlotte Erlanson-Albertsson. 2005. Overeating of palatable food is associated with blunted leptin and ghrelin response. Regulatory Peptides., vol 130 pp 123-132.; Charlotta Dornonville de la Cour, Andreas Lindqvist, Emil Egecioglu, YC Loraine Tung, Vikas Surve, Claes Ohlsson, Charlotte Erlanson-Albertsson, Suzanne Dickson L and Rolf Håkanson. 2005. Ghrelin treatment reverses the reduction in weight gain and body fat in gastrectomized mice. Gut, vol 54 pp 907-913.; Andreas Lindqvist, Paul Mohapel, Brenda Bouter, Helena Frielingsdorf, Donald Pizzo, Patrik Brundin and Charlotte Erlanson-Albertsson. 2006. High-fat diet impairs hippocampal neurogenesis in male rats. European Journal of Neurology, (inpress); Andreas Lindqvist, Charlotta Dornonville de la Cour, Rolf Håkanson and Charlotte Erlanson-Albertsson. . Ghrelin affects gastrectomy-induced decrease in UCP1 and beta3-AR mRNA expression in mice. (manuscript); Andreas Lindqvist, Annemie Baelemans and Charlotte Erlanson-Albertsson. . Effect of sucrose, glucose and fructose in liquid form on serum ghrelin and leptin levels. (manuscript)
• id: e725b9f8-a7c2-43bc-a5b4-0c7ad8182a68 (old id 547535)
• date added to LUP: 2016-04-01 16:04:42
• date last changed: 2018-11-21 20:38:32