Les glucocorticoïdes (GC) sont des substances très utilisées en thérapeutique, mais parfois détournées de leur utilisation première par les sportifs en raison de leurs effets ergogéniques. Si les effets secondaires d’une prise chronique de GC sont bien connus, les répercussions d’un traitement court restent controversées. Nous nous sommes tout d’abord intéressés aux effets d’un traitement d’1 semaine de GC (50-60 mg/j de prednisone/prednisolone) sur la prise alimentaire, la composition corporelle, la glycémie, l’insulinémie et la sécrétion d’adipokines chez des sujets masculins et féminins sportifs de loisir. Pour des raisons éthiques, cette étude n’a pu être conduite chez des sportifs de haut-niveau. Les adipokines (i.e., leptine et adiponectine) apparaissent significativement augmentées chez tous les sujets par le traitement de GC, mais celui-ci n’entraîne aucune modification de la prise alimentaire, de la composition corporelle ou de l’insulinémie. Il n’existe pas d’effet genre à l’exception de l’hyperglycémie mise en évidence sous GC uniquement chez les sujets de sexe masculin. Il apparait également qu’un traitement d’une semaine de prednisone per os n’altère que de manière très transitoire l’axe hypothalamo-hypophyso-surrénalien, avec un retour à des concentrations basales de cortisol et de DHEA seulement 3 jours après la fin du traitement. / Glucocorticoids (GC) are substances widely used in therapy, but sometimes diverted from their primary use by athletes for their ergogenic effects. Whereas the side effects of chronic use of GC are well known, the impact of short treatment remains controversial. We first investigated the effects of 1 week treatment of GC (50-60 mg/day of prednisone/prednisolone) on food intake, body composition, blood glucose, insulinemia, and adipokine secretion in male and female recreationally-trained athletes. For ethical reasons, this study could not be conducted in elite athletes. The adipokines (ie, leptin and adiponectin) appear significantly increased in all subjects after the GC treatment, but the treatment does not induce any change in food intake, body composition or insulin concentrations. There is no gender effect with the exception of hyperglycemia demonstrated with GC only in males. It also appears that the short-term treatment of oral prednisone alters the hypothalamic-pituitary-adrenal axis only very transient, with a return to basal levels of cortisol and DHEA only 3 days after of treatment.

Leucine injections directly into the brain decrease food intake whereas supplementation of this amino acid in a diet has a negligible effect on food intake. We sought to investigate why orally supplemented leucine is ineffective as an anorexigen. We found that mice consuming leucine exhibited increased cFos immunoreactivity in the ARC and PVN of hypothalamus, areas controlling energy balance. However, real time- PCR analysis of the hypothalamic tissue in mice that were exposed to oral leucine showed changes in expression of genes involved in the regulation of energy balance as well as those mediating feeding reward (TMEM18, MC4R, CRH, FTO, SLC6A15, DOR). This suggests that leucine consumption affects activity of not only brain pathways that control calorie intake, but also those that mediate eating for pleasure. Hence the lack of feeding response to leucine supplementation in a diet may stem from the simultaneous action of this amino acid at brain circuit promoting reward and energy homeostasis.

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Three studies were designed to investigate the hypothesis that physiological and environmental variables are both independent and interactive in determining food intake (FI) in children and adolescents during puberty (8 – 18 y old). Study 1 investigated the effect of obesity, sex and pubertal status on appetite hormones in response to a mixed glucose and whey protein (WP) drink in adolescents. Obese adolescents had higher insulin, PYY and lower ghrelin than normal weight (NW) controls, with a more pronounced effect in males. Puberty did not affect insulin, but the change in PYY in response to the drink was greater and ghrelin was lower in mid-late pubertal than pre-early pubertal obese males. To further describe the role of puberty, Study 2 examined the effect of pubertal status on FI following consumption of glucose and WP drinks in male and female children. In mid-late pubertal children, mealtime compensation for energy from glucose was less at 60 than at 30 min, but not for whey. However, compensation for either drink was not different at 30 and 60 min meals in pre-early pubertal children. Finally to demonstrate the interaction between puberty and environmental influences on FI, Study 3 examined the effect of distraction (television viewing, TVV) while eating and pubertal status on food intake after a pre-meal glucose drink in girls. In Study 3, TVV had no effect on FI, however, glucose suppressed FI more with no TVV compared with TVV (24% vs. 10%). In postpubertal girls, glucose reduced FI by ~27% in both the no TVV and TVV conditions, but in peripubertal girls, reduction in FI was 22% without TVV and only 1% while TVV. Thus, the results of this research support the hypothesis that physiological and environmental variables are both independent and interactive in determining FI in children and adolescents during puberty.

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A theory of growth and feed intake in the pig is proposed and the results of five experiments to test it are reported here. An attempt is first made to describe the potential growth in pigs, that is, growth under non-limiting conditions; the conditions needed to allow potential growth to be retained are then considered. Two ways of providing non-limiting feeding conditions are discussed: a single balanced feed and a set of feeds given as a choice. In addition, a model which predicts the voluntary feed intake of pigs is also developed and tested in experiments. The results from pigs offered single feeds in the first two experiments were consistent with the predictions of the model, which were that the rate of feed intake would increase as the protein content of the feeds was decreased. The size of the increase depended on the ability of the pig to lose heat. In these experiments, when pigs were offered a pair of feeds as a choice, a combination of which was non-limiting, the results suggested that this method cannot be successfully used to attain the potential growth of pigs. The diet selection results were characterised by a considerable variation in the diets selected by individual pigs, and only some pigs achieved what was estimated to be their potential rate of growth. It was suggested that pigs which failed to select a non-limiting diet did not have the necessary chance to choose. Experiment 3 evaluated a simple method of ensuring that pigs are given both the necessary choice, and the chance to choose. This was achieved by giving them the opportunity to sample the single feeds, which were to be offered as a choice, alone on alternate days for a short period of six days. Subsequently, pigs given a choice between two feeds were able to select a non-limiting diet. Experiment 4 incorporated the method established previously and consisted of a severe investigation into the rules of diet selection. It was concluded that pigs are able to avoid excess of nutrient, in this case protein, intake or to select the best possible diet in less favourable conditions, ie. a choice between two limiting feeds. The last experiment consisted of an extended test of the theory that a pig will select a diet which is a reflection of its degree of maturity, state and sex. Pigs made fat and delayed in growth in one period were subsequently given the opportunity to recover on a pair of feeds offered as a choice. The diets selected by the fat pigs satisfied their requirements for compensatory protein gain allowing only a slow rate of lipid gain. In addition, they met the different growth and fattening requirements by the two sexes. All these findings are discussed in relation to the use of choice-feeding as an independent test of other estimates of resource requirements, as a feeding technique when the potential growth of pigs is to be observed and as a help in predicting the feeding behaviour in pigs.

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Background: Chemotherapy has side effects that may interfere with food intake. Children suffering from a malignant disease are subjected to treatment with chemotherapy. They may therefore become at risk of undernutrition during the period of treatment. This in turn may increase the risk of infections, delayed therapy and influence the outcome of treatment. Few studies have investigated how children undergoing chemotherapy for cancer perceive food and eating. Attempts to improve food intake and the nutritional status require an understand-ing of how eating patterns are altered during chemotherapy in children. Study design: Dietary information and anthropometric data were collected after the initiation of chemotherapy in 14 children, consecutively admitted to the Paediatric Haematology and Oncology Unit at Umeå University Hospital. This initial study resulted in the establishment of more flexible mealtime routines on the ward. A follow-up study was conducted with another group of 11 children. Interviews were performed with a third group of 21 consecutively ad-mitted children, their parents and attending nurses. The focus was on the children’s own per-ception of and their parents’ and nurses’ attitudes to their food intake during hospitalisation. Recognition thresholds for the basic tastes were determined with 10 of the oldest of these children and 10 healthy controls. Results: Before introduction of new mealtime routines, the average daily oral energy intake during hospitalisation was 58% of the Swedish Nutrition Recommendations, SNR. The chil-dren had a significant weight loss up to three months after onset of chemotherapy. After the introduction of new mealtime routines, the average daily oral intake on hospital days was 61% of SNR and thus still lower than recommended despite efforts to serve palatable food on the ward. When enteral and parenteral nutrition was included, the energy intake came close to that recommended for healthy children, 91% of SNR. Both children and parents perceived that altered taste was an important cause of the children’s eating problems. The children also viewed food aversions, nausea and vomiting and pain as important causes, while the parents perceived nausea, food aversions and altered smell as significant factors. The nurses on the other hand, viewed nausea, the ward environment, and food rejection as a way of gaining some influence over the situation as important factors. The patients had significantly higher thresholds for bitter taste and significantly more patients made mistakes in taste recognition compared with controls. Conclusion and clinical implication: There seem to be changes both in the sense of taste as well as in the perception of food in children undergoing chemotherapy for malignant disease. Thus, single solutions such as providing a variety of “tasty food” in the hospital setting in order to improve food intake does not suffice for many paediatric cancer patients. The indi-vidual’s food preferences and aversions should be considered and combinations of oral, en-teral and parenteral nutrition support should be provided.