Energetic limits on reproduction: Maternal food intake

We examined the factors influencing maternal food intake and pup growth in Norway rats. Mother rats allowed pups in naturally large litters to grow at a slower rate than pups in naturally small litters. Pups reared by dams in a warm ambience (26°C) gained weight more slowly than dams at 22°C, and maternal food intake but not weight gain was depressed in the high ambient temperature. Pup growth at 18°C was unimpaired, with those dams eating no more and gaining no less weight than dams at 22°C. Nest material, however, was found to be essential for the successful rearing of young at cooler ambient temperatures. While restriction of food during gestation resulted in a marginally lower weight gain for the pups during the first 2 weeks postpartum, the dams appeared not to mobilize corporal stores or increase their food intake during lactation. Heavy body weight mothers did not eat any more, nor did they gain any less weight nor rear larger pups than light body weight dams. Rat mothers increased their consumption of a diet diluted with non-nutritive fiber to equal the nutritive intake of their controls, with their pups not differing in their growth rate. Pups reared by dams eating a high quality diet grew faster than pups with dams on the control diet. Food intake by mother rats is required during lactation relative to the amount of milk that is delivered to the pups, rather than to an absolute amount of food. Lactating females with a concurrent pregnancy neither increase their food intake nor appear to mobilize their corporal stores to deal with the added energetic drain of pregnancy. Indeed, their young grew somewhat more quickly than pups nursed by dams that were simply lactating. Taken as a whole, these results suggest that Norway rat dams apparently do not monitor and defend a maximal pup growth rate. Rather, rat dams seem to continue to defend their own homeostasis, and by doing so, allow the young to grow and survive under a wide variety of circumstances.     

L-tryptophan injection fails to alter nutrient selection by rats

Nutritional studies on rats given a choice between two diets differing in protein content have led to the proposal that brain 5-HT content regulates protein intake [2]. Pharmacologic studies under similar conditions of dietary self-selection suggest that brain 5-HT controls carbohydrate intake [41]. We tested the effect of elevating brain 5-HT via tryptophan injection (100 mg/kg) on short-term food intake and selection by rats choosing between two diets differing in protein and carbohydrate content. Under these conditions neither total food intake nor protein and carbohydrate selection were affected despite increases of 50% in brain concentrations of 5-HT and 5-HIAA. The effect of Trp administration was selective to serotonin metabolism as brain concentrations of NE, DA and DOPAC were not affected. These results suggest that alterations in brain 5-HT content which may occur following meal ingestion may not be of physiological importance in regulating nutrient intake and selection.     

Gastric capacity, test meal intake, and appetitive hormones in binge eating disorder

Binge eating disorder (BED), characterized by ingestion of very large meals without purging afterwards, is found in a subset of obese individuals. We showed previously that stomach capacity is greater in obese than in lean subjects, and in this study, we investigated capacity in obese individuals with BED. We also determined ad-libitum intake of a test meal until extremely full. Furthermore, we measured various appetitive hormones (insulin, leptin, glucagon, CCK, ghrelin) and glucose before a fixed meal and for 120 min afterwards. An acetaminophen tracer was used to assess gastric emptying rate. We compared three groups of overweight women: 11 BED, 13 BE (subthreshold BED), and 13 non-binge-eating normals. The BED individuals had the largest stomach capacity as assessed by either maximum volume tolerated (P=.05) or by gastric compliance to pressure (P=.02) using an intragastric balloon. Although test meal intake did not differ between groups, it correlated (P=.03) with gastric capacity. The BED group showed a tendency (P=.06) to have greater area under the curve (AUC) and had higher values at 5 and 60 min (P<.05) for insulin compared to normals. Moreover, the BED subjects had lower ghrelin baselines premeal, and lower AUC for ghrelin, which then declined less postmeal than for the normals (P<.05). None of the other blood values differed, including glucose, leptin glucagon, and CCK, as well as acetaminophen, reflecting gastric emptying. The lower ghrelin in BED, although contrary to what was expected, is consistent with lower ghrelin in obesity, and suggests down-regulation of ghrelin by overeating. The lack of differences in CCK is consistent with the lack of differences in gastric emptying rate, given that CCK is released when nutrients reach the intestine. The results show that BED subjects have a large gastric capacity as well as abnormalities in meal-related ghrelin and insulin patterns that may be factors in binge eating.     

The Effect of Accuracy of Perceptions of Dietary-Fat Intake on Perceived Risk and Intentions to Change

Consumption of excess fat increases risk for many health problems and diseases. In the present study, 188 undergraduate students were studied to understand self-perceptions of dietary-fat intake and the impact of those perceptions. Findings indicated that the majority of participants had inaccurate perceptions about the amount of fat in their diets. Further, compared to people who overestimated dietary-fat intake, people who underestimated fat intake had lower perceived risk of cancer, had lower intentions to change, and demonstrated less knowledge about the dietary-fat content of many foods. Findings suggest that this unrealistic underestimation of fat intake is a cognitive barrier to dietary change and people who underestimate dietary fat intake may require more intensive intervention to change their diets.     

The nociceptin/orphanin FQ/NOP receptor system as a target for treatment of alcohol abuse: a review of recent work in alcohol-preferring rats

The intracerebroventricular administration of the 17 amino acid peptide nociceptin/orphanin FQ (N/OFQ), the endogenous ligand of the NOP receptor (previously referred to as ORL-1 or OP4 receptor), reduces voluntary 10% ethanol intake in genetically selected Marchigian Sardinian alcohol-preferring (msP) rats. Studies aimed at the pharmacological characterization of the receptor, which mediates the effect, have shown that the C-terminal 13 amino acid sequence is crucial for activity and that the selective NOP receptor antagonist [Nphe(1)]N/OFQ(1-13)NH(2) blocks the effect of N/OFQ on ethanol drinking. In place conditioning studies, N/OFQ abolishes the conditioned place preference (CPP) induced by ethanol in msP rats, or by morphine in nonselected Wistar rats; these findings suggest that N/OFQ is able to abolish the rewarding properties of ethanol and morphine. Moreover, N/OFQ inhibits reinstatement of alcohol-seeking behavior induced to electric footshock stress, as well as reinstatement of alcohol-seeking behavior induced by ethanol-paired cues. Together, these findings suggest that N/OFQ and its receptor may represent an interesting target for pharmacological treatment of alcohol abuse.     

Integrated circuit drop-sensing drinkometer

An casuy constructed and inexpensive drop-sensing drinkometer is described, which incorporates an integrated circuit photodetector. It provides a reliable and convenient means of automatically monitoring fluid intake in a number of experimental situations. The animal is undisturbed and isolated from the electrical system components.     

Electroconvulsive shock effects on food and water intake as a function of prior deprivational state

Two experiments, each using approximately 30 male and 30 female hooded rats, examined the effects of electroconvulsive shock (ECS) on water intake as a function of the water deprivation state of the animal and food intake and body weight as a function of food deprivation state. In Experiment 1, half the animals were subjected to water deprivation prior to ECS or sham ECS, and the other half were watered ad lib; in Experiment 2, food deprivation was the pre-ECS manipulation. As predicted, ECS produced a decrease in water intake in the ad lib watered animals but not in the deprived ones. A similar treatment by deprivation interaction was not found for food intake or body weight. In the males, food intake was decreased for one day by the treatment but recovered to a normal level two days following ECS; however, such an effect of ECS on food intake did not occur in the females. Since food and water intake was not differentially affected by ECS and sham ECS in deprived animals, previous cautions regarding ECS effects on motivational states may not be germane to many studies using appetitive conditioning paradigms.     

Effect of treadmill exercise on food intake and body weight in lean and obese rats

Body weight and food intake of lean and obese, male and female Osborne-Mendel rats following treadmill exercise were compared. Rats were assigned, separately by sex, to one of three diet groups; Group 1 was fed a low fat (10%) diet throughout the study, Group 2 was fed a high fat (55%) diet for 16 weeks and then switched to the low fat diet 1 week prior to exercise, and Group 3 was fed the high fat diet throughout the study. To control for differences in work output between the leanest and heaviest animals, exercise intensity was adjusted across groups such that all exercised rats had equivalent energy expenditure. After a 3 day training period, the exercise was successively increased over 8 days until a work output of 374.9J was reached. Relative to their respective controls, obese exercised males showed a reduction in body weight but no change in food intake. In contrast, exercised females showed no change in body weight or food intake, regardless of dietary condition.     

Influence of a monotonous food on body weight regulation in humans

Four human subjects were fed ad lib with a bland diet for a period of 3 weeks. Their body weight decreased by 3.13 kg during this period. It was observed that the shift of the palatability response to sucrose solutions induced by a gastric glucose load (alliesthesia) was not affected by such a reduction of body weight. This result was compared to a previous experiment showing a decreased alliesthesia after a body weight loss due to the restriction of a palatable diet. These results confirm the role of the palatability of the diet on the maintenance of a body weight level and provide evidence for an interaction between the two factors in determining the oral satiation process.     

Blutdruck,relatives Körpergewicht,Alkoholkonsum und Elektrolytausscheidung in der BRD und der DDR: Die Intersalt-Studie

Summary The relationships between body mass index (BMI) and age, alcohol consumption, 24-hr urinary electrolyte excretion, and BP were studied in 588 subjects from three German centers participating inIntersalt, a highly standardized, previously reported protocol. Men and women aged 20–59 were sampled in Bernried, FRG; Cottbus, GDR; and Heidelberg, FRG. The subjects from the three centers did not differ in BMI, level of education, physical activity, cigarette- or alcohol-consumption patterns, or urinary Cl excretion. Mean Na excretion was 167, 147, and 172 mmol/24 hr in Bernried, Cottbus, and Heidelberg, while mean K excretion was 72, 55, and 73 mmol/24 hr, respectively. The excretion of these electrolytes was significantly lower in Cottbus than in Bernried or Heidelberg. BMI increased progressively in men with age; in women BMI plateaued until the 5th decade, after which it increased to equal that of men. In individual centers, the excretion of electrolytes was correlated with BML Sodium and chloride excretion were highly correlated. The data from each individual center were fitted to a multiple regression model. Age, BMI, sex, and alcohol consumption entered the model.