Energy intake of rats fed a cafeteria diet

The proportion of lipid, carbohydrate and protein energy self-selected by male and female rats from a cafeteria diet has been studied for a 48-day period (36-day in female rats). The diet consisted in 12 different items and was offered daily, in excess and under otherwise standard conditions, to rats--caged in groups of three--from weaning to adulthood. Groups of control animals were studied in parallel and compared with the cafeteria groups. Cafeteria diet fed groups of rats ingested more energy and lowered their metabolic efficiency with age. Male rats ate more than females and increased their body weight even after female practically stopped growing. There was a wide variation in the aliments consumed each day by the cafeteria-fed rats. However, the proportion of lipid, protein and carbohydrate the rats ate remained constant. Male rats ingested more lipid than females. Carbohydrate consumption was constant in control and cafeteria fed groups of rats independently of sex. Protein consumption was higher in cafeteria rats than in controls, but the differences were not so important as with liquid. Fiber content of the cafeteria diet was lower than that of the control diet. The cafeteria diet selected by the rats was, thus, hypercaloric and hyperlipidic, with practically the same amount of carbohydrate than the control diet, slightly hyperproteic and, nevertheless, remarkably constant in its composition with respect to time. Cafeteria rats had a higher water intake than controls. All these trends were maintained despite the observed changes in the animals' tastes and their differential consumption of the ailments of the diet.     

Meal size as a determinant of food intake in normal and hypothalamic obese rats

Size of meals taken by normal rats was greatly increased by following each spontaneously initiated meal with gastric infusion of additional diet. In a second experiment, rats in the dynamic phase of hypothalamic obesity were limited to meals much smaller than the unusually large ones they usually take. In both experiments rats made precise adjustments in meal frequency which maintained daily food intakes at or close to pre-experimental levels.     

Effect of a high-carbohydrate diet intake on muscle glycogen repletion after exercise in rats previously fed a high-fat diet

Summary The effect of a high-carbohydrate (C) diet intake on muscle glycogen repletion during the early period of recovery from exercise was studied in rats previously fed a high-fat (F) diet. In experiment 1, 3 weekold male and in experiment 2, 3 week-old female rats were used. Rats were fed either the F or the C diet for 2–10 weeks ad libitum and then were meal-fed regularly twice a day for 25 days in experiment 1, or for 5 weeks in experiment 2. During the period of regular feeding, half of the rats in both dietary groups continued to eat as before (F-F and C-C) but the other half of the rats were switched to the counterpart diets (F-C and C-F) in experiment 1. In experiment 2, half of the F-F group were switched to the C diet (F-C) for 3, 7, and 14 days after the period of regular feeding. Pre-exercise glycogen content in soleus, red gastrocnemius, and heart muscles and liver was higher in rats fed the C diet (C-C and F-C) than in rats fed the F diet (F-F and C-F) in experiment 1. Glycogen repletion in red muscle 2 h after the ingestion of a glucose and citrate (3.0 and 0.5 g, respectively, per kg body mass) drink was also higher in the former than in the latter. There was a positive relationship in skeletal muscles between pre-exercise glycogen content and the rate of glycogen repletion. Compared with the rats maintained on the F diet (F-F), the rats switched to the C diet (F-C) for 3 and 7 days showed faster glycogen repletion in soleus and/or red gastrocnemius muscles in experiment 2. These results indicated that the poor capacity of restoration of skeletal muscle glycogen in rats previously fed the F diet was improved by the short-term dietary switch to the C diet.     

Subcutaneous glycerol injection fails to reduce food intake in rats fed a high protein diet

To test whether glycerol utilization might contribute to glycerol-induced hypophagia, cumulative food intake was measured following subcutaneous glycerol injection in rats fed a high carbohydrate (HC), a high fat (HF) or a high protein (HP) diet, because food composition is known to influence the activity of several glycerol metabolizing enzymes. In additional experiments, the effect of glycerol injection on plasma glycerol, blood glucose, and liver glycogen levels was also investigated in HC-, HF-, and HP-rats. Subcutaneous glycerol injection (6.3 mmoles/kg b.w.) significantly reduced food intake in HC- and HF-rats, but failed to decrease feeding in HP-rats. Five hours after glycerol injection, plasma glycerol levels were significantly elevated in HP-rats, but did not differ from the glycerol levels of controls in HC- and HF-rats. Subcutaneous glycerol injection did not affect blood glucose concentration or liver glycogen content 5 hours after injection in any feeding group. The results suggest that oxidation of the injected glycerol might contribute to the glycerol-induced hypophagia in HC- and in HF-rats.     

Reproduction and organ weight responses in female rats fed a restricted balanced diet or a restricted nonprotein calorie diet with or without supplemental glutamine or cysteine

Primiparous Sprague-Dawley rats were used in two experiments to test the hypothesis that restriction of carbohydrate and fat calories alone versus comparable restriction of a balanced diet through gestation produces differential effects on gastrointestinal tract, reproductive tract and conceptus development. Rats were assigned on d 1 of pregnancy (13 rats/diet) to the following diets in Expt. 1: (1) balanced control diet fed ad libitum, C; (2) control diet fed at 50% of ad libitum intake, R; (3) restricted nonprotein energy diet containing twice the concentrations of protein, vitamins and mineral elements as the balanced control diet but fed at 50% of ad libitum intake of control diet, RCal; (4) R diet modified plus 0.21% L-cysteine, R + Cys; (5) R diet modified plus 1.54% L-glutamine, R + Glu. In Expt. 2, the treatment groups were: (1) Control diet, C; (2) C diet fed at 50% of ad libitum, R; (3) RCal diet fed at 50% of ad libitum intake of C; (4) RCal diet plus 2% L-glutamine fed at 50% of ad libitum intake of C. All pregnant rats were euthanized on d 20 postcoitum. Body weight of control dams was greater (P less than .01) than that of other dams in both experiments. Uterus weight and litter weight were less in RCal than in other dams in both experiments.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of tea catechins on body fat accumulation in rats fed a normal diet

Although it is known that tea catechins exert potent effects in obese subjects, there is scant information concerning these effects on body weight gain and body fat accumulation in the non-obese. We studied normal rats fed a normal diet and water containing either 0.1% or 0.5% tea catechins to examine the effects on body fat content and serum cholesterol levels, as well as evaluating whether the effect is related to bile acids, which in recent years have emerged as an inducer of energy expenditure. The administration of 0.5% catechins decreased the accumulation of body fat and the serum levels of cholesterol and bile acids. These results indicate that tea catechins modulate lipid metabolism not only in obese subjects, but also in the non-obese.     

Comparison of DNA contents of visceral organs in rats with ventromedial hypothalamic lesions and fed a high fat diet

Bilateral lesions of ventromedial hypothalamus are followed by a number of changes including vagal hyperactivity and hyperinsulinemia. To investigate if cell proliferation occurs in visceral organs in rats with ventromedial hypothalamic (VMH) lesions and fed a high fat diet, we determined DNA contents of visceral organs (liver, pancreas, small and large intestines, spleen, kidney and heart) 1 and 4 week after VMH lesions or start of high fat diet. In rats with VMH lesions, DNA contents increased significantly in liver, pancreas, and small and large intestines at 1 week, and maintained the same levels until the 4th week. DNA contents increased most in the pancreas, followed by small and large intestines, and liver. DNA content did not change in spleen, kidney, or heart. In rats fed a high fat diet, there was no increase in the DNA content of these organs, except in the small intestine at 4 weeks. The results suggest that VMH lesions produce excessive DNA synthesis in visceral organs, whereas a high fat diet does not. VMH lesions may induce cell proliferation in visceral organs through vagal hyperactivity and/or changes of humoral growth factors.     

Influence of diet palatability on the meal taking behavior of hypothalamic hyperphagic and normal rats.

Female rats made hyperphagic by parasagittal hypothalamic knife cuts overate a palatable milk diet by greatly increasing their meal size, while meal frequency was only slightly increased. Reducing the palatability of the diet by quinine or salt adulteration decreased to normal levels the total intake and meal size, but not meal frequency of hyperphagic rats. The disruption in the diurnal feeding pattern displayed by the hyperphagic rats was relatively unaffected by diet palatability changes. The results are discussed in terms of the short and long term regulatory deficits thought to be responsible for the hypothalamic hyperphagia syndrome.     

Effect of diet consistency, taste and calories on food intake of weanling rats with dorsomedial hypothalamic lesions

Male weanling Sprague-Dawley rats with dorsomedial hypothalamic lesions (DMNL rats) primarily destroying the dorosomedial hypothalamic nuclei (DMN) showed significant hypophagia on lab chow chunks compared to sham-operated controls. When given a choice between lab chow in the form of chunks or powder, both controls and DMNL rats ate similar amounts of lab chow powder while DMNL rats ate less lab chow chunks. Total caloric consumption was the same as on chunks alone. When returned to lab chow chunks as the only source of calories, the pattern and magnitude of intake was again depressed for the DMNL rats. When offered a choice between Ginger Snaps cookies in chunk form versus powder, DMNL rats remained hypophagic in terms of chunk consumption while the intake from powder was similar in both controls and DMNL rats. When offered a choice between chunks of lab chow and Ginger Snaps, DMNL rats were again hypophagic on lab chow chunks, ate the same as the controls of the cookies, and the total caloric intake was of the same magnitude and pattern as observed in previous tests. The data suggest, but do not conclusively show, that DMNL rats are not hypophagic because they have an aversion to chewing hard food and that, when offered a diet similar in hardness to lab chow chunks i.e., hard cookies, will prefer the less tasty but nutritionally complete lab chow. They are apparently capable of choosing a diet for complete nutrition and, as previously reported, can meter calories competently.     

Learned aversions in rats fed a tryptophan-free diet

Rats maintained for ten days on a tryptophan-free diet (TRP-FREE) consumed significantly less food than rats receiving the same diet supplemented with L-tryptophan (TRP-SUPP). On Day 11, both groups of rats were given a 24-hour two-diet preference test which allowed them to choose between the pre-exposed diet and a novel alternative. TRP-FREE rats displayed significantly lower preferences than TRP-SUPP rats for the pre-exposed diet. Reduced preferences were still present after animals had been allowed a week of free access to nutritionally adequate chow. The results suggest that the declines in food intake induced by a tryptophan-free diet may be based on learned aversions.     

Intact regulation of protein intake during the development of hypothalamic or genetic obesity in rats

Adult female rats made hyperphagic with bilateral lesions of the medial hypothalamus as well as spontaneously hyperphagic adult female rats of the Zucker strain were studied for their abilities to regulate dietary protein and energy intakes. This was accomplished by permitting both models of animal obesity to select freely between two isocaloric diets containing 10% vs 60% by weight casein (protein) for at least one month. Compared to appropriate control groups, both experimental groups became obese by consuming more of the low protein diet and less of the high protein diet. The overall effect of this selection pattern was an excessive intake of energy in the form of carbohydrate and fat while maintaining control levels of protein intake. These data imply that the stimulus for hyperphagia in both animal models of obesity is some physiological and/or behavioral error in energy regulation but not protein regulation.     

Effects of lateral hypothalamic lesions on food intake of rats during exposure to cold

Lateral hypothalamic damage impaired both physiological and behavioral responses of rats during exposure to a 5 degree C environment. The brain-damaged animals usually did not conserve heat in the cold as well as control rats did, nor did they always increase their caloric intake to meet their energy needs. However, when given sucrose solution to drink instead of water, they did increase their ingestion of chow in response to cold exposure. It is likely that the elevated consumption of palatable fluid served to relieve dehydration and thereby removed its constraints on eating, thus permitting hyperphagia to occur. In contrast to these results, rats with large dopamine-depleting brain lesions, produced by intraventricular 6-hydroxydopamine treatments, always increased food intake when exposed to cold stress and demonstrated no apparent problems in peripheral vasoconstriction. Thus, it is unlikely that striatal dopamine depletions account for either the impaired feeding response or the inadequate heat conservation of rats with lateral hypothalamic lesions during cold stress.     

Salt and water intake in Brattleboro rats with hypothalamic diabetes insipidus

Brattleboro rats lacking vasopressin have an elevated plasma osmolality and a stimulated renin-angiotensin system relative to Long-Evans rats (LE). The current studies were performed to elucidate the factors controlling water and salt intake in the Brattleboro rat with diabetes insipidus (DI). DI and LE rats were given the choice of water and saline solutions ranging from 0.1-1.0% to assess palatability, dialyzed with isotonic glucose to test for sodium appetite after sodium depletion, and infused intracranially with an angiotensin II analogue (saralasin) to assess the role of angiotensin II in spontaneous salt and water intake. DI rats exhibited spontaneous salt intake which was not significantly different from LE rats and increased their intake of 3.0% NaCl following sodium depletion, although less reliably than LE rats. A significant proportion of those DI rats not developing a sodium appetite showed attenuation of their diabetes following dialysis. No evidence for involvement of angiotensin II in spontaneous salt and water intake was found.     

Food intake and growth of rats fed with adiurnal periodicity

The effects of adiurnal periodicity of feeding on the food intakes and growth of rats kept under a 12-hr light-dark cycle or continuous light were examined. When rats were fed for 5 hr once every 20 hr or for 7 hr once every 28 hr, they ate less food and grew more slowly than rats that were fed for 6 hr once every 24 hr, regardless of the lighting conditions. The data are discussed in terms of the relation between the feeding cycle and the internal circadian clock.     

Food intake control and RNA content of hypothalamic neurons in infant rats

The influence of glycerol, glucose and lysine administration on the total RNA content in individual neurons of the ventromedial hypothalamus (VMH) and lateral hypothalamus area (LHA) in infant male rats was studied. Sixty minutes after administration, the total RNA content of the VMH neurons significantly decreased--from 13th day after glycerol and from 17th day after the glucose and lysine administration. The total RNA content of LHA neurons significantly increased from 17th day after glycerol and glucose and on 25th day after lysine administration. The noted changes of the RNA content, and especially the changes of the RNA proportion in these hypothalamic regions are well corresponding with the onset of the hypophagic effect of glycerol, glucose and amino acids in infant rats. The oppositional changes of the RNA content of VMH and LHA neurons are in conformity with the different role of these hypothalamic centers in food intake control.