Atrial natriuretic peptide and feeding activity patterns in rats

This review presents historical data about atrial natriuretic peptide (ANP) from its discovery as an atrial natriuretic factor (ANF) to its role as an atrial natriuretic hormone (ANH). As a hormone, ANP can interact with the hypothalamic-pituitary-adrenal axis (HPA-A) and is related to feeding activity patterns in the rat. Food restriction proved to be an interesting model to investigate this relationship. The role of ANP must be understood within a context of peripheral and central interactions involving different peptides and pathways

Anxiogenic-like effect of acute and chronic fluoxetine on rats tested on the elevated plus-maze

The selective serotonin reuptake inhibitor fluoxetine (FLX) is widely prescribed for depression and anxiety-related disorders. On the other hand, enhanced serotonergic transmission is known to be classically related to anxiety. In this study, the effects of acute (5.0 mg/kg) and chronic (5.0 mg/kg, 22 days) FLX were investigated in both food-deprived and non-deprived rats tested in the elevated plus-maze. Significant main effects of the three factors (drug, food condition and administration regimen) were observed, but no interaction between them. The administration of either acute or chronic FLX resulted in an anxiogenic effect, as detected by a significant reduction in the percentage of time spent in the open arms and in the percentage of open arm entries. Food deprivation yielded an anxiolytic-like profile, probably related to changes in locomotor activity. The administration regimen resulted in an anxiolytic profile in chronically treated rats, as would be expected after 22 days of regular handling. The anxiogenic action of acute FLX is consistent with both its neurochemical and clinical profile. The discrepancy between the anxiogenic profile of chronic FLX and its therapeutic uses is discussed in terms of possible differences between the type of anxiety that is measured in the plus-maze and the types of human anxiety that are alleviated by fluoxetine.

Involvement of the caudal raphe nuclei in the feeding behavior of rats

Involvement of the caudal raphe nuclei (raphe pallidus, RPa; raphe magnus, RMg, and raphe obscurus, ROb) in feeding behavior of adult rats was studied by measuring c-Fos protein expression, in animals submitted to the "meal-feeding" model of food restriction in which the rats were fed ad libitum only from 7:00 to 9:00 h, for 15 days. The experimental groups submitted to chronic fasting, named 'search for food' (SF), 'ingestion of food' (IF) and 'satiety of food' (SaF) were scheduled after a previous study in which the body weight and the general and feeding behaviors were evaluated by daily monitoring. Acute, 48-h fasting (AF) was used as control. In the chronic group, the animals presented a 16% reduction in body weight in the first week, followed by a continuous, slow rise in weight over the subsequent days. Entrainment of the sleep-wake cycle to the schedule of food presentation was also observed. The RPa was the most Fos immunopositive nucleus in the chronic fasting group, followed by the RMg. The ANOVA and Tukey test (P<0.05) confirmed these results. The IF group was significantly different from the other three groups, as also was the number of labeled cells in the RPa in SF and IF groups. Nevertheless, no significant difference was observed between RMg and RPa, or RMg and ROb in the SaF and AF. However, it is interesting to observe that the groups in which the animals were more active, searching for or ingesting food, presented a larger number of labeled cells. These results suggest a different involvement of the caudal raphe nuclei in the somatic and autonomic events of feeding behavior, corroborating the functions reported for them earlier.

Can calories from ethanol contribute to body weight preservation by malnourished rats?

Our objective was to compare the use of calories from ethanol by well-nourished and malnourished rats in terms of body weight. Female Wistar rats weighing 170-180 g at the beginning of the study were used. The animals were divided into two groups (N = 12 each): group W received water ad libitum and group E an ethanol solution ad libitum as the only source of liquid throughout the experiment. The concentration of ethanol was increased weekly from 0 to 5, 10, 20 and 40% (v/v). In the well-nourished phase (A), all rats received food ad libitum (AW and AE). Ethanol treatment (AE) was then interrupted and water was offered to both groups. After 2 weeks both AW and AE rats were submitted to food restriction (50% of group AW food consumption), thus initiating the malnutrition phase (M). Liquid was offered as described before to the same W (MW) and E (ME) groups. The weight gain during the 1-week treatment of AE rats was similar to that of AW animals only when AE rats received the 5% (v/v) ethanol solution (9.16 vs 10.47 g). Weight loss was observed after exposure to 10% ethanol (P < 0.05) in spite of maintenance of caloric intake. Malnourished rats presented weight loss, which was attenuated by ethanol intake up to the 20% (v/v) solution and was related to an increased caloric offer. This effect was not observed with the 40% ethanol solution (-9.98 g). These data suggest that calories from ethanol were used to maintain body weight up to the concentration of 10% (v/v) (well-nourished) and 20% (v/v) (malnourished) and that ethanol has a toxic profile which depends on nutritional status.

Modalities of exercise training on liver fat accretion and inflammatory markers in ovariectomized rats

Les facteurs de risque des maladies cardiovasculaires, telle, que la détérioration du profil lipidique, deviennent plus prononcés après la ménopause, ce qui fait de la maladie coronarienne, l’une des principales causes de décès chez les femmes ménopausées. Une proportion importante de femmes prennent du poids après la ménopause en particulier dans la région abdominale entraînant par conséquent des perturbations métaboliques. Des données récentes suggèrent également que l’absence des œstrogènes observée à la ménopause favorise le développement de la stéatose hépatique. Cette dernière a été incriminée pour incriminée dans le développement de la résistance à l'insuline, et est de ce fait considérée comme une composante hépatique du syndrome métabolique. Il est impératif d'établir des stratégies visant à contrecarrer l'accumulation de graisse dans le foie et l’accroissement du tissu adipeux chez les femmes ménopausées, en tenant compte que l'utilisation de l'hormonothérapie substitutive est de nos jours moins soutenue. Les quatre études de la présente thèse ont été conduites pour tenter de fournir des informations sur le traitement et la prévention de l’augmentation de la masse graisseuse et de la stéatose hépatique qu’entraîne la suppression des œstrogènes, à travers les modifications du mode de vie (diète et exercice physique) chez la rate ovariectomizée (Ovx); un modèle animal de la ménopause. Dans les deux premières études nous nous sommes concentrés sur l’augmentation de la masse graisseuse et sa reprise suite à une perte de poids. Dans la première étude, nous avons montré que les rates Ovx qui ont suivi un programme de restriction alimentaire (FR) ont diminué significativement (P < 0.01) leur poids corporel, leur contenu en graisses intra-abdominales ainsi que leurs triacylglycérols (TAG) hépatiques, comparativement aux rates Ovx nourries à la diète normale. De plus, l’entraînement en résistance (RT) a prévenu la reprise de poids corporel ainsi que l’accroissement du tissu adipeux et l’accumulation de lipides dans le foie des rates Ovx, après l’arrêt du régime amaigrissant. Les résultats de la deuxième étude ont confirmé l'efficacité de la restriction alimentaire associée à l’entraînement en résistance (FR + RT) dans la réduction du poids corporel, des lipides dans le foie et le tissu adipeux chez les rates Ovx. Tenant compte des résultats de notre première étude, l’entraînement en résistance seulement a constitué un atout pour atténuer le poids corporel et la masse grasse reprise par les rates Ovx suite à un programme de perte de poids (FR + RT); bien que l'impact ait été moindre comparé au maintien seul de la restriction alimentaire. De la même manière que la supplémentation en œstrogènes, les résultats de la troisième étude indiquent que l'entraînement en endurance mené concurremment avec l’ovariectomie a significativement atténué l'accumulation de lipides dans le foie ainsi que dans le tissu adipeux. Toutefois, l’entraînement en endurance effectué avant l'ovariectomie n'a pas protégé contre l'accumulation des graisses qu’entraîne l'ovariectomie, si celui-ci est interrompu après l'ovariectomie. Enfin, pour compléter les résultats antérieurs, nous avons montré dans la quatrième étude que l’expression des gènes impliqués dans la synthèse de lipide; SREBP-1c, SCD-1, ChREBP, et ACC dans le foie a augmenté après le retrait des œstrogènes, tandis qu’une diminution (P < 0.01) des niveaux d'ARNm de PPAR-α a été observée. De plus, l'expression hépatique des gènes des cytokines pro-inflammatoires incluant IKKβ, IL-6 ainsi que le contenu protéinique de NF-кB étaient augmentés (P < 0.01) chez les rates Ovx par rapport aux rates ayant subi une Ovx simulée (Sham). Toutes ces perturbations ont été améliorées avec la supplémentation en œstrogènes seulement, ainsi qu'avec l'entraînement en endurance seulement. Dans l'ensemble, nos résultats indiquent que l'exercice physique (en résistance ou en endurance) a un impact significatif sur la réduction de l'accumulation des lipides dans le foie et dans le tissu adipeux des rates Ovx. De plus, chez les rates Ovx, l’entraînement en endurance mimerait les effets des œstrogènes sur l'expression des gènes impliqués dans l'accumulation de lipides et l’inflammation préclinique dans le foie.

Skeletal muscle fibre plasticity in response to selected environmental and physiological stimuli

Skeletal muscle constitutes a highly adaptable and malleable tissue that responds to environmental and physiological challenges by changing its phenotype in terms of size and composition, outcomes that are brought about by changes in gene expression, biochemical and metabolic properties. Both the short- and long-term effects of nutritional alterations on skeletal muscle homeostasis have been defined as the object of intensive research over the last thirty years. This review focuses predominantly on assimilating our understanding of the changes in muscle fibre phenotype and functional properties induced by either food restriction or alternatively existing on a high fat diet. Firstly, food restriction has been shown in a number of studies to decrease the myofibre cross sectional area and consistently, it has been found that glycolytic type IIB fibres are more prone to atrophy than oxidative fibres. Secondly, in rodents, a high fat diet has been shown to induce an oxidative profile in skeletal muscle, although obese humans usually show higher numbers of glycolytic type IIB fibres. Moreover, attention is paid to the effect of prenatal maternal food restriction on muscle development of the offspring in various species. A key point related to these experiments is the timing of food restriction for the mother. Furthermore, we explore extensively the seemingly species-specific response to maternal malnutrition. Finally, key signalling molecules that play a pivotal role in energy metabolism, fibre type transitions and muscle hypertrophy are discussed in detail.

Plastic and evolutionary responses to heat stress in a temperate dung fly: negative correlation between basal and induced heat tolerance?

Extreme weather events such as heat waves are becoming more frequent and intense. Populations can cope with elevated heat stress by evolving higher basal heat tolerance (evolutionary response) and/or stronger induced heat tolerance (plastic response). However, there is ongoing debate about whether basal and induced heat tolerance are negatively correlated and whether adaptive potential in heat tolerance is sufficient under ongoing climate warming. To evaluate the evolutionary potential of basal and induced heat tolerance, we performed experimental evolution on a temperate source 4 population of the dung fly Sepsis punctum. Offspring of flies adapted to three thermal selection regimes (Hot, Cold and Reference) were subjected to acute heat stress after having been exposed to either a hot-acclimation or non-acclimation pretreatment. As different traits may respond differently to temperature stress, several physiological and life history traits were assessed. Condition dependence of the response was evaluated by exposing juveniles to different levels of developmental (food restriction/rearing density) stress. Heat knockdown times were highest, whereas acclimation effects were lowest in the Hot selection regime, indicating a negative association between basal and induced heat tolerance. However, survival, adult longevity, fecundity and fertility did not show such a pattern. Acclimation had positive effects in heat-shocked flies, but in the absence of heat stress hot-acclimated flies had reduced life spans relative to nonacclimated ones, thereby revealing a potential cost of acclimation. Moreover, body size positively affected heat tolerance and unstressed individuals were less prone to heat stress than stressed flies, offering support for energetic costs associated with heat tolerance. Overall, our results indicate that heat tolerance of temperate insects can evolve under rising temperatures, but this response could be limited by a negative relationship between basal and induced thermotolerance, and may involve some but not other fitness-related traits.

Patterns of fos activation in rat raphe nuclei during feeding behavior

To analyze the differential recruitment of the raphe nuclei during different phases of feeding behavior, rats were subjected to a food restriction schedule (food for 2 h/day, during 15 days). The animals were submitted to different feeding conditions, constituting the experimental groups: search for food (MFS), food ingestion (MFI), satiety (MFSa) and food restriction control (MFC). A baseline condition (BC) group was included as further control. The MFI and MFC groups, which presented greater autonomic and somatic activation, had more FOS-immunoreactive (FOS-IR) neurons. The MFI group presented more labeled cells in the linear (LRN) and dorsal (DRN) nuclei; the MFC group showed more labeling in the median (MRN), pontine (PRN), magnus (NRM) and obscurus (NRO) nuclei; and the MFSa group had more labeled cells in the pallidus (NRP). The BC exhibited the lowest number of reactive cells. The PRN presented the highest percentage of activation in the raphe while the DRN the lowest. Additional experiments revealed few double-labeled (FOS-IR+ 5-HT-IR) cells within the raphe nuclei in the MFI group, suggesting little serotonergic activation in the raphe during food ingestion. These findings suggest a differential recruitment of raphe nuclei during various phases of feeding behavior. Such findings may reflect changes in behavioral state (e.g., food-induced arousal versus sleep) that lead to greater motor activation, and consequently increased FOS expression. While these data are consistent with the idea that the raphe system acts as gain setter for autonomic and somatic activities, the functional complexity of the raphe is not completely understood. (c) 2008 Elsevier B.V. All rights reserved.

Opposite effects of fasting on TGF-beta 3 and T beta RI distribution in the gastric mucosa of suckling and early weanling rats

Objective: Our aim was to evaluate the effects of a dietary regimen (suckling or early weaning) and feeding status (fed or fasted) on the distribution of transforming growth factor-beta 3 (TGF-beta 3) and TGF receptor-I (T beta RI) in the gastric epithelium of pups Methods: Wistar rats were used At 15 d, half of the pups were separated from dams and fed with hydrated powered chow On day 17, suckling and early weanling rats were subjected to fasting (17 h). Four different conditions were established. suckling fed and fasted and early weanling fed and fasted At 18 d stomachs were collected under anesthesia and were fixed in 4% formaldehyde for immunohistochemistry The number of immunostained epithelial cells per microscopic field was determined for TGF-beta 3 and T beta RI in longitudinal sections from the gastric mucosa Results: We found that during suckling, fasting reduced the number of immunolabeled cells per field of both molecules when compared with the fed group (P < 0.05), whereas in early weaning, food restriction increased TGF-beta 3 and T beta RI distributions (P < 0.05) We also observed that TGF-beta 3 and T beta RI were more concentrated in parietal cells in the upper gland in suckling pups, whereas after early weaning these were displaced to parietal and chief cells at the bottom of the gland Conclusion: Suckling and early weaning directly influence TGF-beta 3 and T beta RI distributions in the gastric epithelium in response to fasting, such that early weaning anticipates the effects observed in adult rats. Furthermore, the differential concentrations of TGF-beta 3 and T beta RI indicate that they might be important for cell proliferation events in growth control (C) 2010 Elsevier Inc. All rights reserved

Fasting differentially regulates plasma corticosterone-binding globulin, glucocorticoid receptor, and cell cycle in the gastric mucosa of pups and adult rats

Ogias D, de Andrade Sa ER, Kasai A, Moisan M, Alvares EP, Gama P. Fasting differentially regulates plasma corticosterone-binding globulin, glucocorticoid receptor, and cell cycle in the gastric mucosa of pups and adult rats. Am J Physiol Gastrointest Liver Physiol 298: G117-G125, 2010. First published October 15, 2009; doi:10.1152/ajpgi.00245.2009.-The nutritional status influences gastric growth, and interestingly, whereas cell proliferation is stimulated by fasting in suckling rats, it is inhibited in adult animals. Corticosterone takes part in the mechanisms that govern development, and its effects are regulated in particular by corticosterone-binding globulin (CBG) and glucocorticoid receptor (GR). To investigate whether corticosterone activity responds to fasting and how possible changes might control gastric epithelial cell cycle, we evaluated different parameters during the progression of fasting in 18- and 40-day-old rats. Food restriction induced higher corticosterone plasma concentration at both ages, but only in pups did CBG binding increase after short-and long-term treatments. Fasting also increased gastric GR at transcriptional and protein levels, but the effect was more pronounced in 40-day-old animals. Moreover, in pups, GR was observed in the cytoplasm, whereas, in adults, it accumulated in the nucleus after the onset of fasting. Heat shock protein (HSP) 70 and HSP 90 were differentially regulated and might contribute to the stability of GR and to the high cytoplasmic levels in pups and elevated shuttling in adult rats. As for gastric epithelial cell cycle, whereas cyclin D1 and p21 increased during fasting in pups, in adults, cyclin E slowly decreased, concomitant with higher p27. In summary, we demonstrated that corticosterone function is differentially regulated by fasting in 18-and 40-day-old rats, and such variation might attenuate any possible suppressive effects during postnatal development. We suggest that this mechanism could ultimately increase cell proliferation and allow regular gastric growth during adverse nutritional conditions.

Estratégia alimentar com ciclos de restrição e realimentação no desempenho produtivo de juvenis de tilápia do Nilo da linhagem GIFT

O objetivo deste estudo foi avaliar a ocorrência de resposta compensatória no desempenho produtivo de juvenis de tilápia do Nilo Oreochromis niloticus, linhagem GIFT, submetidos a diferentes estratégias alimentares. Foram utilizados 135 juvenis de tilápia, distribuídos em nove tanques de polietileno de 100L cada. As estratégias testadas foram: grupo controle (alimentado todo dia), grupo alimentado por cinco dias seguidos de dois dias de restrição de alimento (5A/2R) e grupo alimentado por quatro dias seguidos de três dias de restrição de alimento (4A/3R). Foram avaliados parâmetros físico-químicos da água e de desempenho produtivo. Os resultados foram submetidos à análise de variância, e as médias foram comparadas pelo teste Tukey, a 5% de probabilidade. A qualidade de água, o fator de condição e a conversão alimentar não foram influenciados pela estratégia alimentar. O grupo alimentado com a estratégia 5A/2R apresentou peso final, ganho de peso e taxa de crescimento específico semelhantes ao grupo continuamente alimentado (7,8 e 9,2g; 6,4 e 7,8g e 2,7 e 3,0% dia-1, para peso final, ganho de peso e taxa de crescimento especifico, respectivamente). A estratégia 4A/3R apresentou os piores resultados de desempenho produtivo, e a estratégia 5A/2R pode ser usada na alimentação de juvenis de tilápia do Nilo sem prejuízo ao desempenho produtivo, possibilitando inclusive redução de até 22,5% na quantidade de alimento ofertada.

Crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) submetidos à restrição alimentar e realimentação durante um ano

Neste trabalho, avaliou-se o efeito da restrição de ração alternada com realimentação no crescimento, desenvolvimento gonadal e composição muscular de matrinxãs (Brycon cephalus) adultos, de ambos os sexos, durante um ano (janeiro de 1998 a janeiro de 1999). Foram utilizados 135 peixes, separados em dois grupos: controle, alimentado diariamente até aparente saciação, e experimental, submetido ininterruptamente a ciclos de três dias de alimentação/2 dias de restrição de ração (40% de restrição ao mês). Foram realizadas 7 amostragens, nas quais foram utilizados 8 a 10 peixes por grupo. Após anestesia, os peixes foram pesados e as gônadas foram retiradas para determinação do IGS, sexo e fase do ciclo reprodutivo. Porções dos músculos branco e vermelho foram retiradas para determinação da porcentagem de lipídio total, proteína bruta, matéria seca e umidade. Os resultados mostraram que a estratégia alimentar utilizada não afetou o crescimento, o desenvolvimento gonadal e a composição muscular do matrinxã. A restrição de ração seguida por realimentação parece ter desencadeado mecanismos de ajuste metabólico para melhor utilização do alimento e aporte suficiente de energia para o crescimento, processo de maturação gonadal e composição corporal. É possível estabelecer formas de manejo alimentar mais econômicas para o matrinxã sem que processos fisiológicos importantes sejam afetados.

Feeding strategy with alternate fasting and refeeding: effects on farmed pacu production

P>A 36-day trial was conducted to determine the effects of repetitive periods of food restriction and refeeding on growth and energy metabolism in pacu (Piaractus mesopotamicus). A total 264 juvenile fish (36.9 +/- 2.8 g) were fed with the experimental diet for 36 days using three regimes: (i) feeding daily to satiation (FD); (ii) no feed for 3 days, then feeding the same amount offered to the control groups for the next 3 days (NF/R controlled); and (iii) no feed for 3 days, then feeding to apparent satiation for the next 3 days (NF/R at satiation). The treatments were distributed into four tanks each. WG and SGR were higher in FD group. Fish refed showed hyperphagia just up to the second day of refeeding. The worst feed conversion rate and the lowest protein efficiency ratio were found in fish NF/R controlled. The lowest values of visceral fat somatic index were found in both fasted fish groups, particularly in NF/R at satiation. The LL and glycogen concentrations, and the hepatosomatic index were all elevated in both feed restricted fish. Muscle lipid showed a tendency to decrease after the cycle of fasting and refeeding. Plasma free fatty acids and glucose levels were elevated in fish subjected to feeding restrictions while serum triglycerides levels were reduced. Triiodothyronine levels were significantly depressed in fish from the NF/R-controlled group and remained at the same levels as the control fish in fish NF/R at satiation. Results indicated that fish subjected to cyclic periods of 3-day satiation or controlled feeding after 3-days of fasting were unable to achieve the final body weight of fish fed to satiation after 36 days.

Avaliação do crescimento e do custo da alimentação do pacu (Piaractus mesopotamicus Holmberg, 1887) submetido a ciclos alternados de restrição alimentar e realimentação

Avaliaram-se os efeitos da utilização de ciclos alternados de restrição alimentar e realimentação no crescimento do pacu, durante o período de engorda, e a viabilidade desta prática na produção comercial da espécie. Juvenis foram distribuídos em três tanques e submetidos a diferentes manejos alimentares, constituindo os tratamentos: A (alimentado ad libitum), B (restrição alimentar de 4 semanas, realimentado por 9 semanas) e C (6 semanas de restrição alimentar, realimentado por 7 semanas), em um total de 13 semanas por ciclo (4 ciclos experimentais). No final de cada ciclo alimentar, 20 peixes de cada tratamento foram amostrados e os dados biométricos registrados. Os valores obtidos para peso, comprimento total e fator de condição (K) foram submetidos a ANOVA e as médias comparadas pelo teste de Duncan. Os resultados mostraram que o tratamento C é o mais indicado somente para outono/inverno, promovendo maior crescimento, menor custo com ração, baixa conversão alimentar e maior receita líquida parcial. Entretanto, durante as estações mais quentes do ano (primavera/verão) outros programas de alimentação devem ser testados, utilizando-se períodos mais curtos de restrição alimentar. Quando se tratou da produção anual, o tratamento A respondeu melhor em termos de biomassa produzida, apesar do maior gasto com alimentação, visto que, com o aumento da temperatura, o crescimento dos peixes dos demais tratamentos ficou prejudicado.

Desenvolvimento gonadal de fêmeas de matrinxã, Brycon amazonicus, submetidas a restrição alimentar

O presente estudo avaliou o efeito de ciclos de restrição alimentar e realimentação (2/3 dias), aplicados durante seis meses antes da desova, no desenvolvimento gonadal de matrinxã. Na ocasião da desova, fêmeas alimentadas diariamente e submetidas ao regime alimentar experimental, selecionadas para a indução hormonal, foram sacrificadas para retirada das gônadas e do fígado, com os quais se calculou o IGS (índice gonadossomático) e o IHS (índice hepatossomático), sendo os ovários processados para análise histológica. Não houve alteração no peso relativo dos ovários e fígado, e o desenvolvimento gonadal não foi afetado pelo esquema alimentar. Os valores de IGS foram de 5,09±4,98% e 9,79±4,17% e os de IHS foram de 0,84±0,07% e 0,91±0,11%, para as fêmeas controle e experimentais, respectivamente, sem diferenças significativas entre os grupos. Os ovários de peixes dos dois grupos apresentaram as mesmas características do estádio maduro, com predominância de ovócitos na fase final de maturação, repletos de vitelo. O estudo indica que a restrição alimentar não afetou a preparação das fêmeas para a reprodução e que ciclos adequados de restrição e realimentação poderão ser aplicados na criação do matrinxã, assegurando menores custos de produção.