Sandra Lopes de Souza

Perinatal protein restriction reduces the inhibitory action of serotonin on food intake

Early malnutrition has been associated with a high risk of developing obesity, diabetes and cardiovascular diseases in adulthood. In animals, poor perinatal nutrition produces hyperphagia and persistent increased levels of serotonin (5‐HT) in the brain. Inasmuch as 5‐HT is directly related to the negative regulation of food intake, here we have investigated whether the anorexic effects of 5‐HT are altered by protein malnutrition. Pregnant Sprague‐Dawley rats were fed adu2003libitum either a control (20% protein) or a low‐protein (8% protein) diet throughout pregnancy and lactation. At weaning, pups received a standard diet and at 35u2003days their feeding behaviour was evaluated after the administration of dl‐fenfluramine (dl‐FEN), an anorexic compound that blocks the reuptake of 5‐HT and stimulates its release. Male offspring born to protein‐restricted dams exhibited significantly decreased body weight and hyperphagia compared with controls. dl‐FEN dose‐dependently reduced the 1u2003h chow intake at the onset of the dark cycle in both control and undernourished rats. However, the hypophagic effects of dl‐FEN were significantly attenuated in animals submitted perinatally to protein restriction. The stimulatory action of dl‐FEN on c‐fos immunoreactivity within the paraventricular nucleus of the hypothalamus was also decreased in low‐protein‐fed rats. Further pharmacological analysis with selective 5‐HT1B and 5‐HT2C receptor agonist showed that the reduced anorexic effects of 5‐HT in malnourished animals were coupled to a desensitization of 5‐HT1B receptors. These observations indicate that the hyperphagia associated with metabolic programming is at least partially related to a reduced regulatory function of 5‐HT on food intake.

Perinatal undernutrition-induced obesity is independent of the developmental programming of feeding

Protein or calorie restriction during gestation and/or suckling induces hyperphagia and increases the susceptibility to develop obesity, glucose intolerance and hypertension in adulthood. The mechanisms by which early nutrient restriction affects the normal physiological regulation of feeding as well as to what extent the metabolic programming of hyperphagia contributes to the long-term risk of obesity and insulin resistance remain, however, to be determined. Here the temporal pattern of food intake and the behavioural satiety sequence were investigated in the offspring of Sprague-Dawley rats fed a control (C) or a low-protein (LP) diet throughout pregnancy and lactation. During the first two months of their post-natal life, protein-restricted animals exhibited hyperphagia characterized by a delayed appearance of satiety, an increase in meal size and reduced latency to eat. Protein-restricted pups also exhibited an enhanced expression of the orexigenic peptides Agouti-related protein and neuropeptide Y and decreased hypothalamic levels of the anorexigenic peptide pro-opiomelanocortin. At 8 months, LP rats still consumed larger meals than their control counterparts but they ingested daily the same amount of food as control offspring and exhibited enhanced abdominal fat and increased levels of triglycerides and fatty acids in serum. These observations indicate that the hyperphagia observed in young LP rats results from a decreased action of negative feedback signals critical to meal termination and an enhanced function of the positive signals that initiate and maintain eating. These results also suggest that perinatal malnutrition programmes obesity through a mechanism independent of its effects on feeding behaviour.

Nutritional programming in the rat is linked to long-lasting changes in nutrient sensing and energy homeostasis in the hypothalamus.

Background Nutrient deficiency during perinatal development is associated with an increased risk to develop obesity, diabetes and hypertension in the adulthood. However, the molecular mechanisms underlying the developmental programming of the metabolic syndrome remain largely unknown. Methodology/Principal Findings Given the essential role of the hypothalamus in the integration of nutritional, endocrine and neuronal cues, here we have analyzed the profile of the hypothalamus transcriptome in 180 days-old rats born to dams fed either a control (200 g/kg) or a low-protein (80 g/kg) diet through pregnancy and lactation. From a total of 26 209 examined genes, 688 were up-regulated and 309 down-regulated (P<0.003) by early protein restriction. Further bioinformatic analysis of the data revealed that perinatal protein restriction permanently alters the expression of two gene clusters regulating common cellular processes. The first one includes several gate keeper genes regulating insulin signaling and nutrient sensing. The second cluster encompasses a functional network of nuclear receptors and co-regulators of transcription involved in the detection and use of lipid nutrients as fuel which, in addition, link temporal and nutritional cues to metabolism through their tight interaction with the circadian clock. Conclusions/Significance Collectively, these results indicate that the programming of the hypothalamic circuits regulating energy homeostasis is a key step in the development of obesity associated with malnutrition in early life and provide a valuable resource for further investigating the role of the hypothalamus in the programming of the metabolic syndrome.

Sertraline delays the somatic growth and reflex ontogeny in neonate rats

This study investigated the somatic maturation and ontogeny of reflexes in neonate rats treated with sertraline (Sert) during the suckling period. The animals were divided into four groups; three that received daily doses of Sert (5, 10 or 15 mg/kg s.c.; groups Sert5, Sert10, and Sert15, respectively), and a fourth group that received distilled water (Dw) (1 ml/kg/b.w.). Growth indicators (body weight, axis of the head and tail length) were measured daily, from the 1st to the 21st postnatal day. The reflexes (righting, free-fall righting, negative geotaxis, cliff avoidance, auditory startle response, vibrissa placing and palm grasp) and physical-feature maturation (ear unfolding, auditory conduit opening, irruption of the lower incisors and eye opening) were recorded each day of the animals life. All groups were compared to the Dw group. The body weight gain was reduced in all the Sert groups. Moreover, a delay in the growth of the body length was observed in all the Sert groups. Higher Sert doses reduced the speed of growth in the tail length. The medio-lateral head axis reduced in Sert15 and Sert5 doses. Otherwise, Sert10 had a temporary acceleration in this growth, but the growth of the anteroposterior head axis had a delay in all the Sert groups. The highest doses induced a delay in physical-feature maturation. The palm grasp reflex (disappearance) was retarded in Sert10; cliff avoidance advanced in Sert10; negative-geotaxis and free-fall righting retarded in Sert15. The findings suggest that altered serotonergic system activity induced by sertraline early in life could play a role in the retardation of the somatic growth ontogeny as well as a delay in the maturation of some reflexes.

Can physical exercise during gestation attenuate the effects of a maternal perinatal low-protein diet on oxygen consumption in rats?

A protocol of physical exercise, based on maximal oxygen uptake , for female rats before and during pregnancy was developed to evaluate the impact of a low‐protein diet on oxygen consumption during gestation and growth rate of the offspring. Virgin female Wistar rats were divided into four groups as follows: untrained (NT, n= 5); trained (T, n= 5); untrained with low‐protein diet (NT+LP, n= 5); and trained with low‐protein diet (T+LP, n= 5). Trained rats were submitted to a protocol of moderate physical training on a treadmill over a period of 4 weeks (5 days week−1 and 60 min day−1, at 65% of ). At confirmation of pregnancy, the intensity and duration of the exercise was reduced. Low‐protein groups received an 8% casein diet, and their peers received a 17% casein diet. The birth weight and growth rate of the pups up to the 90th day were recorded. Oxygen consumption , CO2 production and respiratory exchange ratio (RER) were determined using an indirect open‐circuit calorimeter. Exercise training increased by about 20% when compared with the initial values (45.6 ± 1.0 ml kg−1 min−1). During gestation, all groups showed a progressive reduction in the resting values. Dams in the NT+LP group showed lower values of resting than those in the NT group. The growth rate of pups from low‐protein‐fed mothers was around 50% lower than that of their respective controls. The T group showed an increase in body weight from the 60th day onwards, while the NT+LP group presented a reduced body weight from weaning onwards. In conclusion, physical training attenuated the impact of the low‐protein diet on oxygen consumption during gestation and on the growth rate of the offspring.

Maternal low-protein diet-induced delayed reflex ontogeny is attenuated by moderate physical training during gestation in rats.

We evaluated the effects of moderate- to low-intensity physical training during gestation on reflex ontogeny in neonate rats whose mothers were undernourished. Virgin female Wistar rats were divided into four groups as follows: untrained (NT, n 7); trained (T, n 7); untrained with a low-protein diet (NT+LP, n 7); trained with a low-protein diet (T+LP, n 4). Trained rats were subjected to a protocol of moderate physical training on a treadmill over a period of 4 weeks (5 d/week and 60 min/d, at 65 % of VO₂max). After confirming the pregnancy, the intensity and duration of the exercise were reduced. Low-protein groups were provided with an 8 % casein diet, and controls were provided with a 17 % casein diet. Their respective offspring were evaluated (during the 10th-17th days of postnatal life) in terms of physical feature maturation, somatic growth and reflex ontogeny. Pups born to mothers provided with the low-protein diet during gestation and lactation showed delayed physical feature and reflex maturation and a deficit in somatic growth when compared with controls. However, most of these deficiencies were attenuated in pups of undernourished mothers undergoing training. In conclusion, physical training during gestation attenuates the effects of perinatal undernutrition on some patterns of maturation in the central nervous system during development.

Modulatory role of serotonin on feeding behavior

Abstract The appearance, the odor, and the flavor of foods, all send messages to the encephalic area of the brain. The hypothalamus, in particular, plays a key role in the mechanisms that control the feeding behavior. These signals modulate the expression and the action of anorexigenic or orexigenic substances that influence feeding behavior. The serotonergic system of neurotransmission consists of neurons that produce and liberate serotonin as well as the serotonin-specific receptor. It has been proven that some serotonergic drugs are effective in modulating the mechanisms of control of feeding behavior. Obesity and its associated illnesses have become significant public health problems. Some drugs that manipulate the serotonergic systems have been demonstrated to be effective interventions in the treatment of obesity. The complex interplay between serotonin and its receptors, and the resultant effects on feeding behavior have become of great interest in the scientific community.

Effects of early weaning on the circadian rhythm and behavioral satiety sequence in rats

The objective of this work was to study the effect of early weaning on circadian rhythm and the behavioral satiety sequence in adult rats. Male Wistar rat pups were weaned for separation from the mother at 15 (D15), 21 (D21) and 30 (D30) days old. Body weight and food intake was measured every 30 days until pups were 150 days old. At 90 days of age, the circadian rhythm of food intake was evaluated every 4h for three days. Behavioral satiety was evaluated at 35 and 100 days of age. This work demonstrated that body weight and food intake were not altered, but the behavioral satiety sequence demonstrated that the D15 group delayed satiety compared with the D30 group at 100 days of age. In the circadian rhythm of the food intake study, early weaning (D15) changed food intake in the intermediary period of the light phase and in the intermediary period of the dark phase. In conclusion, our study showed that early weaning may alter the feeding behavior mainly in relation to satiety and the circadian rhythm of feeding. It is possible that the presence of other environmental stimuli during early weaning can cause hyperphagia and deregulate the mechanisms of homeostasis and body weight control. This study supports theories that depict insults during early life as determinants of chronic diseases.

Short- and long-term effects of a neonatal low-protein diet in rats on the morphology of the larynx

OBJECTIVEnThe aim of this study was to investigate the short- and long-term effects of a maternal low-protein diet during lactation on offspring laryngeal morphology. Our hypothesis was that a neonatal low-protein diet during the critical period of development alters micro- and macroscopic structures of the larynx in adult rats.nnnMETHODSnMale Wistar rats were assigned to a control (casein 17%, n=24) or low-protein (casein 8%, n=24) group according to their mothers diet during lactation. Body weight gain and growth rate were recorded throughout the experiment. The larynx was removed from offspring at days 22 and 60 of life. The anteroposterior and laterolateral lengths of the cartilages epiglottis, thyroid, and cricoid were measured by a digital caliper. The supraglottis, glottis, infraglottis, and vocal cords were stained by hematoxylin-eosin and their structures were analyzed by a Scion Image Beta 4.0.2 program.nnnRESULTSnPups from mothers fed a low-protein diet showed a lower body weight gain. The laterolateral and anteroposterior lengths of the larynx were shorter in undernourished offspring at 22 d old. There were no differences in the structure of the supraglottis, glottis, and infraglottis between groups except for keratinization in pups from undernourished mothers. The microstructure of the vocal cords was changed only at 60 d old.nnnCONCLUSIONnMacroscopic structures of the larynx are sensitive to short-term effects of a neonatal low-protein diet. Vocal cord development can be studied within the context of programming because their microscopic structures are sensitive to the long-term effects of a low-protein diet during lactation.

Early weaning programs rats to have a dietary preference for fat and palatable foods in adulthood

The objective of this work was to study the effect of early weaning on alimentary preference for the macronutrients protein, carbohydrate and fat in adult rats. Male Wistar rat pups were weaned by separation from the mother at 15 (D15) or 30 (D30) days old. Body weight and food intake were measured every 30 days until pups were 150 days old. At 110 days of age, the alimentary preference was evaluated for 1h on 3 consecutive days. At 120 days of age, the palatable diet test was conducted during 3 consecutive 24-h periods. Body weight and food intake were not altered, but early weaning in rats induced an alimentary preference to fat and hyperphagia of a palatable diet. In conclusion, early weaning, although did not modify body weight or basal food intake, promoted an increased preference for palatable and fatty foods. This demonstrates that early weaning is not capable of promoting perceptible alterations of alimentary behavior under normal laboratory conditions. However, in the presence of a stimulating factor such as a choice of nutrients or a palatable diet, a possible latent effect on dietary preferences may become apparent. Over the long term, this preference for foods with high caloric density can lead to obesity and metabolic perturbations.