Increase In Daily Food Intake Research Articles

Modulation of feeding by chronic rAAV expression of a relaxin-3 peptide agonist in rat hypothalamus

Relaxin-3 is a neuropeptide that is abundantly expressed by discrete brainstem neuron populations that broadly innervate forebrain areas rich in the relaxin-3 G-protein-coupled-receptor, RXFP3. Acute and subchronic central administration of synthetic relaxin-3 or an RXFP3-selective agonist peptide, R3/I5, increase feeding and body weight in rats. Intrahypothalamic injection of relaxin-3 also increases feeding. In this study, we developed a recombinant adeno-associated virus 1/2 (rAAV1/2) vector that drives expression and constitutive secretion of bioactive R3/I5 and assessed the effect of intrahypothalamic injections on daily food intake and body weight gain in adult male rats over 8 weeks. In vitro testing revealed that the vector rAAV1/2-fibronectin (FIB)-R3/I5 directs the constitutive secretion of bioactive R3/I5 peptide. Bilateral injection of rAAV1/2-FIB-R3/I5 vector into the paraventricular nucleus produced an increase in daily food intake and body weight gain (P<0.01, ~23%, respectively), relative to control treatment. In a separate cohort of rats, quantitative polymerase chain reaction analysis of hypothalamic mRNA revealed strong expression of R3/I5 transgene at 3 months post-rAAV1/2-FIB-R3/I5 infusion. Levels of mRNA transcripts for the relaxin-3 receptor RXFP3, the hypothalamic 'feeding' peptides neuropeptide Y, AgRP and POMC, and the reproductive hormone, GnRH, were all similar to control, whereas vasopressin and oxytocin (OT) mRNA levels were reduced by ~25% (P=0.051) and ~50% (P<0.005), respectively, in rAAV1/2-FIB-R3/I5-treated rats (at 12 weeks, n=9/8 rats per group). These data demonstrate for the first time that R3/I5 is effective in modulating feeding in the rat by chronic hypothalamic RXFP3 activation and suggest a potential underlying mechanism involving altered OT signalling. Importantly, there was no desensitization of the feeding response over the treatment period and no apparent deleterious health effects, indicating that targeting the relaxin-3-RXFP3 system may be an effective long-term therapy for eating disorders.

Digestibility of nutrients and aspects of the digestive physiology of the greater cane rat, journalThryonomys swinderianus journalin two seasons

The greater cane rat, Thryonomys swinderianus, utilizes high fibrous plant material and is an important meat source in West Africa. An insight in its digestive physiology will enhance our understanding of its feeding habits. Digestibility coefficients of the food were determined during two seasons before the animals were euthanased. The distribution and concentrations of nutrients and energy in different parts of the gastrointestinal tract were determined at the time of day when animals practised coprophagy. Trial 1 diet in the wet season consisted of 36% neutral detergent fibre (NDF), 11% protein and 49% dry matter, while the Trial 2 diet in the dry season consisted of 53% NDF, 8–9% protein and 89% dry matter. The Trial 2 animals on the poor diet increased their daily nutrient intake, possibly increased the volume of digesta and practised frequently cophrophagy, so that faecal production was reduced and digestibility coefficients were relatively high. Coprophagy increased both protein and energy intake as soft pellets in the distal colon had higher protein and energy content than the hard faeces. Energy, protein and acid-detergent fibre were retained in the caecum of Trial 1 females and the caecum and proximal colon of the Trial 2 animals 16 hours after feeding, illustrating the importance of these two regions in the fermentation process. Water was absorbed in the distal colon as dry matter content of digesta increased 53%, 4% and 56% from the proximal colon to the distal colon. Animals produced hard faeces with only 16% and 5% lower moisture content in the dry season, compared to that produced in the wet season, as water was not a limiting factor during the trials. It was concluded that an increase in daily food intake, an increase in coprophagy and the presence of a colonic separation mechanism (that retains small particles) enable the greater cane rat to utilize high fibrous plant material. These digestive strategies seem to be comparable to those observed in other hystricomorph rodents.

Digestibility of Nutrients and Aspects of the Digestive Physiology of the Greater Cane Rat,Thryonomys swinderianusin Two Seasons

The greater cane rat, Thryonomys swinderianus, utilizes high fibrous plant material and is an important meat source in West Africa. An insight in its digestive physiology will enhance our understanding of its feeding habits. Digestibility coefficients of the food were determined during two seasons before the animals were euthanased. The distribution and concentrations of nutrients and energy in different parts of the gastrointestinal tract were determined at the time of day when animals practised coprophagy. Trial 1 diet in the wet season consisted of 36% neutral detergent fibre (NDF), 11% protein and 49% dry matter, while the Trial 2 diet in the dry season consisted of 53% NDF, 8–9% protein and 89% dry matter. The Trial 2 animals on the poor diet increased their daily nutrient intake, possibly increased the volume of digesta and practised frequently cophrophagy, so that faecal production was reduced and digestibility coefficients were relatively high. Coprophagy increased both protein and energy intake as soft pellets in the distal colon had higher protein and energy content than the hard faeces. Energy, protein and acid-detergent fibre were retained in the caecum of Trial 1 females and the caecum and proximal colon of the Trial 2 animals 16 hours after feeding, illustrating the importance of these two regions in the fermentation process. Water was absorbed in the distal colon as dry matter content of digesta increased 53%, 4% and 56% from the proximal colon to the distal colon. Animals produced hard faeces with only 16% and 5% lower moisture content in the dry season, compared to that produced in the wet season, as water was not a limiting factor during the trials. It was concluded that an increase in daily food intake, an increase in coprophagy and the presence of a colonic separation mechanism (that retains small particles) enable the greater cane rat to utilize high fibrous plant material. These digestive strategies seem to be comparable to those observed in other hystricomorph rodents.

A Study of the Nutritional Behavior and Body Mass Indexes for Students of Age (17-25) Years In Baghdad, Iraq.

The aim of this study was to assess the nutritional status for samples at the age of 17-15 years. These samples were taken from secondary schools and universities in Baghdad area, 123 of them were male and 261 were female. Data on weight, height and body mass index (BMI) were determined in each individual. Smaller sample of 215 individuals (male and female) from the original sample was taken in order to record their nutritional behavior and daily food intake during the 24 hours prior to the visit through personal meeting using special questionnaire. The results showed that the weight and the height were within the range of the people of neighboring Arab countries, who are in the same age. Beside 44.4- 55.95% of these samples were within the normal weight using body mass index. Percentages of obesity and overweight were between 43.5- 6.5% for male and female respectively. There was an increase in daily food intake in general for essential diet and energy indeed, as recorded in nutritional behavior. 67% of samples have their breakfast every day. There were 51% of the samples having snacks (additional meal) between the major meals everyday and 62% have beverages every day. Also high percentage of samples were having milk and its products, vegetables, fruits (as nutritional sources) every day and the percentages were 47%, 67%, 78% respectively. In general their nutritional behavior and daily food intake were within the limits which showed by American recommended daily dietary, still there was some incorrect nutritional behavior which need more education and learning about nutrition.

A Study of the Nutritional Behavior and Body Mass Indexes for Students of Age (17-25) Years In Baghdad, Iraq.

The aim of this study was to assess the nutritional status for samples at the age of 17-15 years. These samples were taken from secondary schools and universities in Baghdad area, 123 of them were male and 261 were female. Data on weight, height and body mass index (BMI) were determined in each individual. Smaller sample of 215 individuals (male and female) from the original sample was taken in order to record their nutritional behavior and daily food intake during the 24 hours prior to the visit through personal meeting using special questionnaire. The results showed that the weight and the height were within the range of the people of neighboring Arab countries, who are in the same age. Beside 44.4- 55.95% of these samples were within the normal weight using body mass index. Percentages of obesity and overweight were between 43.5- 6.5% for male and female respectively. There was an increase in daily food intake in general for essential diet and energy indeed, as recorded in nutritional behavior. 67% of samples have their breakfast every day. There were 51% of the samples having snacks (additional meal) between the major meals everyday and 62% have beverages every day. Also high percentage of samples were having milk and its products, vegetables, fruits (as nutritional sources) every day and the percentages were 47%, 67%, 78% respectively. In general their nutritional behavior and daily food intake were within the limits which showed by American recommended daily dietary, still there was some incorrect nutritional behavior which need more education and learning about nutrition.

Effect of Isocaloric Diets and Sibutramine on Food Intake, Body Mass Variation and Serum TNF-α Levels in Rats

Background/Aim: The effect of isocaloric diets and sibutramine on dietary behaviour and TNF-α is poorly understood. The aim of the study was to investigate the effects of isocaloric diets and sibutramine on food intake, body mass variation and serum TNF-α in free-feeding rats. Methods: Three groups of male Wistar rats (n = 63) were fed a high-fat diet, high-carbohydrate diet or high-protein diet for 13 weeks. In the last 3 weeks, each group was divided into 3 subgroups. Each subgroup received sibutramine 5 mg/kg, sibutramine 10 mg/kg or vehicle. Food intake was measured daily during the last week of the experiment; serum TNF-α was assayed and the body weight increasing rate was calculated. Results: The high-fat diet was associated with increased food intake, a greater weight gain ratio and increased TNF-α levels. Sibutramine treatment did not affect the dietary behaviour of high-protein- or high-carbohydrate-fed rats, while it significantly attenuated the daily food intake and body weight gain rate in the high-fat group, at the dose of 10 mg/kg. TNF-α levels were not affected by sibutramine. Conclusions: High-fat feeding was associated with an increase in daily food intake, TNF-α levels and body weight gain rate, as well as with enhanced responsiveness to the anorectic effects of sibutramine. However, sibutramine did not affect TNF-α.

Impairment in insulin sensitivity after early androgenization in the post-pubertal female rat

A link is known to exist between hyperandrogenicity and insulin resistance in mammals. We explored whether androgenization, early in reproductive life, in the female rat has any impact on later peripheral insulin sensitivity and parametrial (PM) fat function. Female, 60 day-old, rats were injected (i.m.) with 100 μl of sterile corn oil either alone (CT) or containing 2 mg of testosterone propionate (TP); rats were then used for experimentation at age 120 days. Daily food intake and body weight were recorded. Different groups of CT and TP rats were subjected to a high glucose load test or 24 h fasting for evaluation of changes in circulating levels of several metabolites and body composition. In vitro experiments were run to study the impact of androgenization on isolated PM adipocyte response to insulin. Finally, the direct effect of testosterone on insulin-induced leptin secretion by normal PM adipocytes was also evaluated. Androgenization induced a significant increase in daily food intake and body weight for the first 20 days after treatment. In vivo experiments indicate that TP rats released more ( P < 0.05) insulin than CT animals after high glucose load in order to maintain similar circulating glucose levels, a characteristic accompanied by decreased ( P < 0.05) overall corticoadrenal response in TP rats. Several metabolic responses to fasting were similar in both groups, although impaired adrenal response and changes in body composition were observed only in TP rats. Interestingly, cultured PM adipocytes from TP rats were less ( P < 0.05) sensitive than CT cells to insulin-induced leptin secretion. Also, we found that 48 h exposure of normal PM adipocytes to high testosterone concentration also impaired adipocyte endocrine function. Our study strongly supports that development of insulin resistance, in the female gender, can be established after an early, even transient, hyperandrogenemia.

The Role of Corticosterone in Supporting Migratory Lipogenesis in the Dark‐Eyed Junco,Junco hyemalis: A Model for Central and Peripheral Regulation

The functional role of corticosterone (CORT) in regulating migratory hyperphagia and lipogenesis was investigated in an annual migrant, the dark-eyed junco (Junco hyemalis). Intraperitoneal injections of either dexamethasone (9 microg DXM/500 microL of 5% EtOH in saline, n=10) to inhibit an increase in baseline CORT or saline (5% EtOH, n=9) were given every 48 h for 15 d after transfer from short (10.5L:13.5D) to long (15.5L:8.5D) days. Food intake, body mass, furcular fat deposition scores, and nocturnal migratory activity were recorded for 29 d after photostimulation. Both groups showed the same increase in daily food intake over the study period (DXM=52%, control=41%). Controls began to increase baseline CORT and mass about 2 wk after photostimulation. DXM-treated birds maintained low CORT and did not increase mass or CORT until injections ceased, at which time they gained mass at the same rate shown earlier by controls. DXM-treated birds did not show greater levels of migratory activity despite experiencing an increase in energy intake during the CORT-inhibited period. Collectively, the results support the migration modulation hypothesis, illustrating how an increase in baseline CORT is needed to support the development of migratory condition. We address the apparent conflict with earlier studies on CORT and migratory food intake and propose a model in which migratory hyperphagia is supported by changes in centrally regulated responses to CORT that can occur even if CORT remains low and lipogenesis is regulated predominantly by peripheral mechanisms that require an increase in baseline CORT.

Improvement in food intake and nutritive utilization of protein from Lupinus albus var. multolupa protein isolates supplemented with ascorbic acid

The protein quality of protein isolates from lupin (LPI) ( Lupinus albus var. multolupa), prepared by isoelectric precipitation, was assessed by chemical analysis of protein and amino acids and biological analysis of digestive and metabolic utilization of protein by growing rats. The animals were fed isonitrogenous and isocaloric diets adjusted to meet their nutrient requirements, in which lupin protein isolate was the only protein source, complemented with 0.5% methionine. Different LPIs were prepared with addition, or not, of ascorbic acid as antioxidant. Protein isolates had a protein content of 87.8–98.1%. Manganese content of protein isolates was reduced by 72.8–89.5% compared to the raw seed flour. Results from in vivo experiments showed that addition of 0.5% ascorbic acid to LPI incorporated into diets led to a 82.8% increase in daily food intake, when compared to the non-supplemented LPI, reaching similar values to those obtained with a casein–methionine control diet. Digestive and metabolic utilization of protein from LPI, assessed by nitrogen absorption or apparent digestibility coefficient, and by nitrogen balance or percentage of retained to absorbed nitrogen, respectively, was high, when the dietary intake of animals fed the LPI diets was adequate after addition of 0.5% ascorbic acid, although slightly inferior to the values obtained with a casein–methionine control diet. The high nutritive utilization of protein was reflected in excellent growth and nutritional indices assayed. In conclusion, ascorbic acid supplementation led to an improvement in the palatability of the LPI diets and, therefore, in daily food intake, which was reflected in a higher nutritive utilization of protein and improvement in weight gain and the food transformation index.

Exposure to brackish water, upon feeding, leads to enhanced conservation of nitrogen and increased urea synthesis and retention in the Asian freshwater stingray Himantura signifer

The white-edge freshwater whip ray Himantura signifer is ammonotelic in freshwater, but retains the capacities of urea synthesis and ureosmotic osmoregulation to survive in brackish water. The first objective of this study was to examine whether exposure to brackish water would lead to increases in food intake, and/or conservation of nitrogen in H. signifer upon daily feeding. Results obtained showed that a progressive increase in ambient salinity, from 1 per thousand to 15 per thousand over a 10-day period, did not lead to an increase in daily food intake. However, there were significant reductions in daily rates of ammonia and urea excretion in H. signifer during salinity changes, especially between day 5 (in 10 per thousand water) and day 10 (in 15 per thousand water) when compared to those of the control kept in 1 per thousand water. Consequently, there was a significant decrease in the percentage of nitrogen (N) from the food being excreted as nitrogenous waste (ammonia-N+urea-N) during this period. On day 10, the tissue urea contents in fish exposed to 15 per thousand water were significantly greater than those of fish kept in 1 per thousand water, and the excess urea-N accumulated in the former fish could totally account for the cumulative deficit in excretion of urea-N+ammonia-N during the 10-day period. Thus, it can be concluded that H. signifer is N-limited, and conserved more N from food when exposed to brackish water. The conserved N was converted to urea, which was retained in tissues for osmoregulation. The second objective of this study was to elucidate whether the retention of the capacity of N conservation in H. signifer would lead to an accumulation of urea in fish exposed to not only 15 per thousand water, but also 1 per thousand water, upon feeding. For fish pre-acclimated to 1 per thousand water or 15 per thousand water for 10 days and then fasted for 48 h, the rate of ammonia excretion in fish exposed to 15 per thousand water was consistently lower than that of fish exposed to 1 per thousand water, throughout the 36-h post-feeding period. In addition, the hourly rate of urea excretion in the former was significantly lower than that of the latter between hours 12 and 36. There were postprandial increases in ammonia contents in the muscle, liver, stomach, intestine, brain and plasma of fish kept in 1 per thousand water; but postprandial increases in ammonia occurred only in the liver and brain of fish exposed to 15 per thousand water, and the magnitudes of increases in the latter were smaller than those in the former. Indeed, postprandial increases in tissue urea contents occurred in both groups of fish, but the greatest increase in urea content was observed in the muscle of fish exposed to 15 per thousand water. Taken together, these results indicate that H. signifer in freshwater could be confronted with postprandial osmotic stress because of its capacity of conserving N and increasing urea synthesis upon feeding.

Overweight and Metabolic and Hormonal Parameter Disruption Are Induced in Adult Male Mice by Manipulations During Lactation Period

Neonatal manipulations (10 min of maternal separation plus s.c. sham injection, daily for the first 21 d of life) determine overweight in male adult mice. In this work, we investigated the mechanisms underlying mild obesity and the alteration of caloric balance. Neonatally manipulated mice become overweight after onset of maturity, showing increased fat tissue and hypertrophic epididymal adipocytes. Increase in body weight occurs in the presence of a small increase in daily food intake (significant only in the adult period) and the absence of a decrease in spontaneous locomotor activity, while the calculated caloric efficiency is higher in manipulated mice, especially in adulthood. Fasting adult animals show hyperglycemia, hyperinsulinemia, hypertriglyceridemia, hypercholesterolemia, and hyperleptinemia. Soon after weaning and in the adulthood, plasma corticosterone and adrenocorticotropin (ACTH) are also significantly increased. Thus, neonatal manipulations in nongenetically susceptible male mice program mild obesity, with metabolic and hormonal alterations that are similar to those found in experimental models of diabetes mellitus, suggesting that this metabolic derangement may have at least part of its roots early on in life and, more interestingly, that psychological and nociceptive stimuli induce these features.

Meeting the energy demands of reproduction in female koalas, Phascolarctos cinereus: evidence for energetic compensation.

Koalas are generally considered to be limited by their ability to acquire energy from their diet of Eucalyptus foliage and have the lowest mass-specific peak lactational energy output measured in any mammal to date. This study considered the energetics and sources of energy utilised for reproduction in free-ranging female koalas. Energy requirements and foliage intake were greater in both lactating and non-lactating females in winter than summer, presumably due to demands of thermoregulation. Koalas met the peak energy requirements of lactation primarily by a 36% increase in their intake of foliage. Metabolic energy expenditure (field metabolic rate, 1778 kJ.day(-1) for a 6.25-kg female at the time of peak lactation) was not elevated during lactation. This was due to compensation for part of their lactational demands by reduction of another, non-reproductive, component of their energy budget. The observed energetic compensation was probably due primarily to substitution of the waste heat from the metabolic costs of milk production and increased heat increment of feeding for thermoregulatory energy expenditure. There may also have been energetic compensation by reduction of some aspect of maintenance metabolism. Such energetic compensation, together with the strategy of spreading lactation over a long period, minimises the magnitude of lactational energy demands on koalas, and thus the increase in daily food intake required during lactation. As the nutritional requirements of females at peak lactation are the highest of any members of the population, low reproductive requirements effectively increase the types and amount of habitat able to support koala populations.

Chronic CNS administration of Agouti-related protein (Agrp) reduces energy expenditure.

To investigate whether the Agouti-related protein (Agrp), the melanocortin receptor antagonist, alters oxygen consumption, as a measure of energy expenditure. A 7-day intracerebroventricular administration of Agrp (1 nmol/day) in rats. Oxygen consumption was determined in closed-circuit respirometers on days 1 and 8. BRL-35135, a beta3-adrenoreceptor agonist known to activate the brown adipose tissue (BAT) thermogenesis directly and increase core temperature, was administered i.p. (40 microg/kg) on day 9 to challenge functionally the BAT. Agrp treatment caused a 54% increase in daily food intake and a 12% increase in body weight. An 8% decrease in VO(2) measurements was observed following ICV Agrp treatment on day 1. A similar decrease (7%) was observed on day 8. BRL-35135 stimulated colonic temperature in control rats. However, in the rats that had previously been treated with Agrp this effect was significantly blunted. Chronic CNS administration of Agrp decreases oxygen consumption and decreases the capacity of BAT to expend energy. The obesity observed following CNS administration of Agrp is the result of decreased energy expenditure and increased food intake.

Leptin reduces food intake but does not alter weight regain following food deprivation in the rat.

When animals are allowed free access to food following an extended period of food restriction, body weight is steadily restored to the pre-food restriction level, ie to a specific body weight 'set-point'. We tested the proposition that leptin is used as a signal by the brain to regulate body weight 'set-point'. To this end, we determined whether long-term leptin infusion in rats would prevent the normal weight regain after food restriction. Male Sprague-Dawley rats received leptin (leptin-treated) or saline (vehicle-treated) by intravenous infusion. After a 2 week run-in period, food intake was adjusted to 50% of each individual's normal intake for 12 days. Two days prior to the return of unlimited access to food, one group of animals received continuous leptin infusion at 3 micro g/h for the next 14 days. Blood samples taken from the tail vein were used to determine leptin concentrations. A third group of animals that did not undergo food restriction but received saline infusion served as control. As leptin acts in the brain to modulate neuropeptide Y (NPY) levels, hypothalamic NPY content was measured at the end of the study. Food restriction to 50% normal intake for 12 days induced a 20% weight loss and significant reductions in plasma leptin compared with non-restricted control rats (0.5+/-0.1 vs 2.6+/-0.4 ng/ml, P<0.05). Intravenous infusion of leptin increased leptin concentrations four-fold compared with vehicle-treated animals (9.5+/-1.3 vs 2.2+/-0.4 ng/ml, P<0.05). The infusion of leptin attenuated the increase in daily food intake after free access to food was resumed (P<0.05 at 4, 6 and 8 days). Despite this, both groups of previously restricted rats had regained the same amount of weight after 12 days of ad libitum feeding. No difference was noted in NPY levels measured in the arcuate nucleus and the paraventricular nucleus, in line with the similar amounts of food eaten by all rats at the end of the experiment. Increasing plasma leptin concentrations just prior to the end of a period of food restriction reduced subsequent food intake, but did not appear to exert a major influence on the body weight 'set-point', as leptin did not prevent weight regain. The results of the present study suggest that leptin may be of little value in maintaining weight loss in individuals who have lost weight through dieting. Further research is required to understand the role of leptin in the regulation of energy balance.

Associations between individual food intake characteristics and indicators of gut physiology of group-housed weanling pigs differing in genotype

AbstractA total of 198, 27-day-old weanling gilts (7·7 kg) were used to study the associations between food intake characteristics measured in individual pigs but which were group-housed, and indicators of gut physiology at 5 days after weaning. All piglets were offered ad libitum access to food and water and were housed in pens (11 piglets per pen) equipped with feeding stations in order to determine the time between weaning and the start of the first food intake (latency time; h), and the increase in daily food intake (daily increase; g/kg0·75per day) for each individual. Forty piglets were selected that either had an early (≤ 2 h) or a late (≥23 h) start of food intake and subsequently either had a relatively fast (≥18 g/kg0·75per day) or slow (≤ 2 g/kg0·75per day) increase in daily food intake so that there were four different groups. Five days after weaning, the 40 piglets were killed in order to determine histological (villous height, crypt depth, number of goblet cells) and functional (maltase and sucrase activities) measures in the proximal small intestine (SI), and microbial measures (ammonia and volatile fatty acid (VFA) concentrations) and dry-matter (DM) content in the distal SI, caecum and colon. Thirteen unweaned piglets were killed to serve as the reference group. Villous height/crypt depth ratio (P &lt; 0·05), number (P &lt; 0·01) of goblet cells on the villi and crypts, and sucrase activity (P &lt; 0·001) in the proximal SI of the unweaned piglets were higher than in the weaned piglets. The proportion of branched-chain VFA (bcVFA; P &lt; 0·01), ammonia-nitrogen (P &lt; 0·001) and DM concentrations (P &lt; 0·01) in the contents of the caecum as well as proportions of bcVFA in the contents of the colon of the unweaned piglets were higher than in the weaned piglets. Apart from a tendency towards an interaction (P &lt; 0·1) between latency time and daily increase with regard to villous height/crypt depth ratio and number of goblet cells on the villi of the proximal SI, histology and function of the proximal SI and digesta characteristics of the distal SI, caecum and colon were not affected by latency time. Piglets with a fast increase in food intake tended to have longer villi on the proximal SI (P &lt; 0·1), and had less acid-mucin containing goblet cells (P &lt; 0·05) on these villi than had the piglets with a slow increase. The piglets with a fast increase had a higher DM content in the colon and tended to have a higher total VFA-concentration in the caecum than did their counterparts with a slow increase. The genotype of the piglets affected maltase (P &lt; 0·01) and sucrase (P &lt; 0·05) activities in the proximal SI and tended to affect the villous height/crypt depth ratio (P &lt; 0·06). Genotype also affected total VFA concentrations (P &lt; 0·05) and tended to affect the ammonia nitrogen (P &lt; 0·1) in the colon and caecum, respectively. This study indicates that within the range of practical food intake levels recorded, the physiology and function of the gut is not markedly affected by the time between weaning and the onset of feeding or by the subsequent increase in daily food intake.

How to get fat: nutritional mechanisms of seasonal fat accumulation in migratory songbirds.

Many migratory birds accumulate large amounts of lipids as the prime energy source for their long-distance flights. This fat accumulation is mostly under endogenous control, reflecting genetically programmed temporal shifts of the body mass set point. It is accompanied by an increase in daily food intake and food utilisation efficiency and by a seasonal shift in food selection. In particular, seasonal frugivory appears to play a key role in many migrants. Fruits have a high content of fatty acids indispensable for building up the specific depot lipids. In addition, plant secondary compounds seem to play some kind of supportive role, but the mechanisms are not yet known. The effect of being fat on the metabolic situation in migrant birds appears to be similar to the metabolic syndrome in obese humans. The fat migratory bird provides a model through which to study nutritional factors as well as the biochemical and endocrine regulation of food intake, body mass and obesity.

Additive effects of lactation and food restriction to increase hypothalamic neuropeptide Y mRNA in rats.

Neuropeptide Y (NPY) is the most powerful appetite stimulant known, and rates of synthesis and release in the hypothalamus correlate closely with nutritional status. Pregnancy and lactation provide an excellent model of physiological hyperphagia. In this study the authors measured food intake, plasma glucose, insulin and luteinizing hormone (LH) and hypothalamic NPY mRNA in rats during pregnancy and in early and late lactation. The effect of food restriction (to 80% of control) during lactation was also studied. Pregnancy resulted in a modest increase in daily food intake over non-lactating controls (controls: 15.6 +/- 0.6 g, pregnant: 19.8 +/- 1.1 g, P < 0.01). During lactation food intake increased dramatically to 355% of non-lactating levels by the 12th day. Insulin and glucose levels were unchanged in lactation, except in the food-restricted animals, when insulin levels were reduced to 49.5 +/- 18.4 pmol/l compared with 215 +/- 55 pmol/l (P < 0.01) in lactating, non-restricted animals, and glucose was reduced to 3.7 +/- 0.2 mmol/l compared with 5.1 +/- 0.2 mmol/l in non-restricted lactating animals. Hypothalamic NPY mRNA was unchanged in pregnancy, moderately increased after 5 days lactation (130 +/- 6.2% of control, P < 0.01) and increased further at 14 days lactation (179 +/- 14%, P < 0.001). The greatest changes occurred in the animals who were food-deprived during lactation, when hypothalamic NPY mRNA levels reached 324 +/- 44% (P < 0.001) of non-lactating levels. Increases in hypothalamic NPY synthesis may be partly responsible for the increase in food intake seen in lactation, but unlike in food deprivation, the increase is not related to circulating insulin, suggesting involvement of other regulatory factors.

Effect of Insulin Treatment or Zinc Supplementation on Vitamin A Status in Streptozotocin-Induced Diabetic Rats.

A Using streptozotocin-induced diabetic rats, we examined the effects of zinc supplementation and insulin treatment on the metabolic availability of vitamin A. All diabetic animals exhibited an elevated plasma glucose (>18 mmol/liter) level within 48 h of intravenous streptozotocin injection. The untreated diabetic rats exhibited a reduction in body weight gain, with a 50% increase in daily food intake. In diabetic animals treated with insulin for 4 weeks, the plasma glucose, body weight gain, and daily food intake were comparable to those of the non-diabetic controls. The plasma concentration of vitamin A was significantly reduced in the diabetic animals, whereas the hepatic content of vitamin A in them was significantly elevated. Treatment with implantable insulin resulted in both plasma and liver concentrations of vitamin A returning to the control non-diabetic levels. Dietary zinc supplementation (120 µg/g diet for 4 weeks) failed to improve the plasma concentration of vitamin A. These results suggest that the impaired metabolic availability of vitamin A in the presence of diabetes is caused by insulin deficiency.

Hepatic portal and vena cava insulin infusions increase food intake in diabetic rats

To test whether the route of insulin delivery has a major effect on the increase in daily food intake associated with chronic insulin treatment, insulin was continuously infused into either the vena cava (VC) or the hepatic portal (HP) vein of 23 diabetic Lewis rats. Increasing insulin doses in both the VC (2 to 6 U/day) and HP (1.5 to 3.5 U/day) groups significantly increased daily food intake ( p < .05). Intake was higher in the VC group at 3 U/day but not at 2U/day. When insulin was delivered at a low fixed dose, daily food intake of both the VC and HP groups only increased after urinary glucose losses increased. The rate of weight gain increased significantly in the VC varied group ( p < .05). Insulin administration also increased energy expenditure ( p < .01). These results suggest that the extent of the increase in daily food intake and body weight that occurs with peripheral exogenous insulin administration is dependent on the route of infusion.

Insulin increases the daily food intake of diabetic rats on high and low fat diets

The effects of insulin dose and diet composition on daily food intake were investigated by IV infusion of insulin in doses of 2 to 5 U/day into diabetic rats consuming either a high CHO or high fat diet. The daily food intake of the diabetic rats on both diets increased significantly over baseline levels ( p < .01) at the low insulin doses and was maintained at these elevated levels through the 5 U/day dose. Insulin increased the rate of weight gain from 1g/day during baseline to 2 and 2.5 g/day in high CHO and high fat fed diabetics ( p < .01). These results show that treatment of diabetic rats with continuous low doses of IV insulin results in a 40% increase in daily food intake regardless of the diet consumed and this increase is accompanied by an increase in rate of body weight gain. While the high fat fed diabetics were relatively hypoglycemic, these increases in intake are not the result of insulin-induced hypoglycemia, since blood glucose concentrations are significantly elevated when the increases occur at the lower insulin doses ( p < .01). Thus, peripheralinsulin infused at physiological levels stimulates rather than inhibits daily food intake.