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PubMed2005

Fasting and refeeding cause rapid changes in intestinal tissue mass and digestive enzyme capacities of Atlantic salmon (Salmo salar L.).

Fasting and refeeding effects on gastrointestinal morphology and digestive enzyme activities of Atlantic salmon, held in tanks of seawater at 9 degrees C and 31 per thousand salinity, were addressed in two trials. Trial 1: Fish (mean body mass 1190 g) were fasted for 40 days and intestines sampled at day 0, 2, 4, 11, 19 and 40. Trial 2: Fish (1334 g), fasted for 50 days, were refed and sampled at day 0, 3 and 7. Mass, length, protein, and maltase, lactase, and leucine aminopeptidase (LAP) activities were analyzed for stomach (ST), pyloric caeca (PC), proximal (PI), mid (MI), and distal intestine (DI). PC contributed 50% of gastrointestinal mass and 75% of enzyme capacity. Fasting decreased mass and enzyme capacities by 20-50% within two days, and 40-75% after 40 days. In PC, specific brush border membrane (BBM) maltase activity decreased whereas BBM LAP increased during fasting. Upon refeeding, enzyme capacities were mostly regenerated after one week. The results suggest that refeeding should start slowly with about 25% of estimated feed requirement during the first 3 days, but may then be stepped up rapidly. Investigations of digestive processes of fed fish should only be performed when intestines are feed-filled to avoid bias due to effects of fasting.

Animal Nutritional Physiological Phenomena↗

PubMed2006

Molecular characterization of lipoprotein lipase, hepatic lipase and pancreatic lipase genes: effects of fasting and refeeding on their gene expression in red sea bream Pagrus major.

To investigate the nutritional regulation of lipid metabolism in fish, molecular characterization of lipases was conducted in red sea bream Pagrus major, and the effects of fasting and refeeding on their gene expression was examined. Together with data from a previous study, a total of four lipase genes were identified and characterized as lipoprotein lipase (LPL), hepatic lipase (HL) and pancreatic lipase (PL). These four lipase genes, termed LPL1, LPL2, HL and PL, share a high degree of similarity. LPL1 and LPL2 genes were expressed in various tissues including adipose tissue, gill, heart and hepatopancreas. HL gene was exclusively expressed in hepatopancreas. PL gene expression was detected in hepatopancreas and adipose tissue. Red sea bream LPL1 and LPL2 gene expression levels in hepatopancreas were increased during 48 h of fasting and decreased after refeeding, whereas no significant change in the expression levels of LPL1 and LPL2 was observed in adipose tissue, indicating that LPL1 and LPL2 gene expression is regulated in a tissue-specific manner in response to the nutritional state of fish. HL and PL gene expression was not affected by fasting and refeeding. The results of this study suggested that LPL, HL and PL gene expression is under different regulatory mechanisms in red sea bream with respect to the tissue-specificities and their nutritional regulation.

Amino Acid Sequence↗

PubMed2004

Molecular cloning of hepatic glucose-6-phosphatase catalytic subunit from gilthead sea bream (Sparus aurata): response of its mRNA levels and glucokinase expression to refeeding and diet composition.

To examine the relationship between structure and function of glucose-6-phosphatase (G6Pase) in fish, we undertook molecular cloning and modulation of G6Pase expression by starvation and refeeding on diets with different nutrient composition in the liver of the carnivorous fish, Sparus aurata. A cDNA encoding the full-length G6Pase catalytic subunit from the liver of S. aurata was isolated. This cDNA encodes a 350-amino acid protein, with low homology to the mammalian G6Pase, although it contains most of the key residues required for catalysis. Based on hydrophobicity and membrane structure prediction, we propose a model containing nine-transmembrane regions for S. aurata G6Pase. Northern blots showed that refeeding after a prolonged starvation rapidly reverses the glucose/glucose-6-phosphate substrate cycle flux in the fish liver through decreased G6Pase expression and strong glucokinase (GK) induction. The effect of refeeding different diets on G6Pase and GK expression, indicated that hepatic intermediary metabolism of fish fed diets with low protein/high carbohydrate diets is impelled towards utilization of dietary carbohydrates, by means of modulation of GK mRNA levels rather than G6Pase expression. These findings challenge the role attributed to dysregulation of G6Pase or GK expression in the low ability of carnivorous fish to metabolise glucose.

Amino Acid Sequence↗

PubMed2006

Refeeding and insulin activate the AKT/p70S6 kinase pathway without affecting IRS1 tyrosine phosphorylation in chicken muscle.

p70 S6 kinase (p70S6K) is a key enzyme involved in the control of protein synthesis. We have previously shown that this kinase is insulin sensitive in chicken muscle despite a relative insulin resistance in the early steps of insulin receptor signaling in this tissue, particularly with no change in tyrosine phosphorylation of the insulin receptor substrate 1 (IRS1). The aim of the present study is to further study the p70S6K pathway in chicken muscle. By analyzing in silico several kinases involved in the protein kinase B (PKB also called AKT)/target of rapamycin (TOR)/p70S6K pathway in the chicken, we showed that the amino acid sequence of the proteins exhibited a very high identity with their homologs in mammalian species and Drosophila. We investigated the regulation of these kinases in vivo or in vitro. Refeeding and insulin treatment significantly (P<0.05) increased the phosphorylation and/or activity of kinases upstream of p70S6K such as AKT and TOR. Similarly, refeeding and insulin increased the phosphorylation of p70S6K on key residues (i.e. T389, T229 and T421/S424) and the phosphorylation of a p70S6K downstream target, the ribosomal protein S6 (by 3-10-fold, P<0.05). Interestingly, we also showed an increase in the phosphorylation level of IRS1 on S632/S635, sites involved in insulin resistance. In conclusion, the AKT/TOR/p70S6K pathway is activated by refeeding and insulin injection, which might negatively regulate IRS1 tyrosine phosphorylation. These results indicate some particularities of the insulin signaling in chicken muscle and suggest the involvement of p70S6K in these features.

Amino Acid Sequence↗

PubMed2004

Attenuation of fasting-induced phosphorylation of mitogen-activated protein kinases (ERK/p38) in the mouse hypothalamus in response to refeeding.

Nutritional status modify the expression of hypothalamic neuropeptides through various signal molecules, including mitogen-activated protein kinases (MAPKs) and cAMP/calcium-responsive element-binding protein (CREB), for the regulation of energy balance. Previously, we demonstrated fasting-induced activation of extracellular signal-regulated kinase 1/2 (ERK) and p38 mitogen-activated protein kinase (p38) in the murine hypothalamus. To study how caloric intake after food deprivation influences intracellular signal transduction, we investigated the phosphorylation of ERK and p38 in the murine hypothalamus of refed mice. In the arcuate nucleus, refeeding significantly attenuated fasting-induced phosphorylation of ERK and CREB. In the paraventricular nucleus, fasting-induced phosphorylation of ERK and p38 was also significantly decreased by refeeding. Thus, refeeding rapidly reduced the fasting-induced phosphorylation of ERK, p38, and CREB, suggesting that the activation of these signal molecules in the hypothalamus is precisely regulated with feeding status.

Animals↗

PubMed2007

Effect of severe undernutrition and subsequent refeeding on gut mucosal protein fractional synthesis in human subjects.

OBJECTIVE: Undernutrition has been associated with gut mucosal atrophy, impaired absorption, and increased permeability. This study investigated the effect of severe undernutrition and subsequent refeeding on gastric and duodenal mucosal protein fractional syntheses (MPFS). METHODS: MPFS was investigated in the gastric body, antrum, and duodenum of 23 severely undernourished patients by means of (14)C-leucine incorporation into tissue protein and repeated after a period of refeeding. Results were evaluated in comparison with a group of 22 healthy controls and presented as mean +/- standard error of the mean. RESULTS: The mean body index of the undernourished patients was 13.29 +/- 0.33 kg/m(2) versus 22.67 +/- 0.63 kg/m(2) in the controls (P < 0.001). MPFS in the controls and undernourished patients were similar (gastric body, 36.49 +/- 2.88 versus 33.41 +/- 3.08%/d; gastric antrum, 25.51 +/- 2.20 versus 24.95 +/- 2.32%/d; duodenum, 25.90 +/- 2.58 versus 25.49 +/- 1.99%/d). After refeeding, the body mass index of the undernourished patients increased to 15.87 +/- 0.44 kg/m(2) (P < 0.001). The MPFS increased significantly (gastric body, 51.80 +/- 8.12%/d, P < 0.05; gastric antrum, 33.44 +/- 3.66%/d, P < 0.05; duodenum, 46.27 +/- 8.02%/d, P < 0.01), with the MPFS of the duodenum significantly greater than the control values (P = 0.01). CONCLUSION: Despite severe undernutrition, MPFS of the gastric body, antrum, and duodenum remained similar to control values. Enteral feeding resulted in a significant increase in MPFS, indicating a trophic response.

Adolescent↗

PubMed2003

Skeletal muscle mitochondrial oxidative capacity and uncoupling protein 3 are differently influenced by semistarvation and refeeding.

We investigated, in skeletal muscle mitochondria isolated from semistarved and refed rats, the relation between the protein expression of uncoupling protein 3 (UCP3) and mitochondrial oxidative capacity, assessed as state 4 and state 3 respiration rates in presence of substrates that are either non-lipids (glutamate, succinate) or lipids (palmitoyl CoA, palmitoylcarnitine). During semistarvation, when whole-body thermogenesis is diminished, state 3 respiration was lower than in fed controls by about 30% independently of substrate types, while state 4 respiration was lower by 20% only during succinate oxidation, but UCP3 was unaltered. After 5 days of refeeding, when thermogenesis is still diminished, neither state 4, state 3 nor UCP3 were lower than in controls. Refeeding on a high-fat diet, which exacerbates the suppression of thermogenesis, resulted in a two-fold elevation in UCP3 but no change in state 4 or state 3 respiration. These results during semistarvation and refeeding, in line with those previously reported for fasting, are not in support of the hypothesis that UCP3 is a mediator of adaptive thermogenesis pertaining to weight regulation, and underscore the need for caution in interpreting parallel changes in UCP3 and mitochondrial oxidative capacity as the reflection of mitochondrial uncoupling by UCP3.

Animal Feed↗

PubMed1999

Regulatory role of glucose-6 phosphatase in the repletion of liver glycogen during refeeding in fasted rats.

We analyzed the biochemical mechanisms involved in the liver glycogen repletion upon refeeding for 360 min in 48 and 96 h-fasted rats. In 48 h-fasted rats, the glycogen synthesis involved a rapid and further sustained induction of glucokinase (GK) (increased twice from 90 min) and a rapid but transient activation of glycogen synthase a (GSa) (maximal increase by 150% at 90 min). It did not involve the inhibition of glycogen phosphorylase a (GPa). In 96 h-fasted rats, the glycogen repletion did not involve the induction of GK for the first 180 min of refeeding. It involved a slow activation of GSa (maximal 150% increase at 180 min) and a rapid inhibition of GPa (significant from 90 min, maximal 50% inhibition by 180 min). In both groups of rats, there was a progressive inhibition of the glucose-6 phosphatase (Glc6Pase) activity (maximal suppression by 30% in both groups at 360 min). These results highlighted a key role for the inhibition of Glc6Pase activity in the liver glycogen repletion upon refeeding.

Animals↗

PubMed2003

[Hypophosphatemia and refeeding syndrome: a severe and underdiagnosed adverse effect].

A 68-year-old woman was hospitalised because of generalised weakness and development of confusional state, related to severe hyponatremia, probably due to an eating disorder with malnutrition. During the first days of hospitalisation the patient eats surprising large amounts of food. The worsening of the confusional state in spite of normalisation of natremia, and the progressive development of anemia and thrombocytopenia, leads to the discovery of a new onset severe hypophosphatemia. The rapid fall in plasma levels of phosphorus, magnesium and potassium are the main futures of the refeeding syndrome. Its clinical manifestations are neurological, muscular, haematological and renal. The development of this syndrome is associated with a high mortality. The refeeding syndrome is seen when carbohydrates are introduced after a period of malnutrition. Identification of patients at risk for the refeeding syndrome (anorexia nervosa, chronic alcoholism, chronic malnutrition, elderly patients, oncology patients), the introduction of cautious progressive nutrition and the careful monitoring of vital signs, electrolytes levels and fluid balance, allows to prevent morbidity and mortality of this syndrome.

Age Factors↗

PubMed1983

Effect of starvation and refeeding on polyamine concentrations and ornithine decarboxylase antizyme in mammary gland of lactating rats.

Starvation caused a marked increase in putrescine content in mammary gland of lactating rats, together with a marked decrease in activity of ornithine decarboxylase and appearance of measurable ornithine decarboxylase antizyme. 2. Refeeding for 5 h caused disappearance of free antizyme and ornithine decarboxylase activity returned to the value in fed animals. Putrescine concentration remained elevated. 3. There was no significant change in nucleic acid content of mammary gland from starved rats, but spermidine and spermine contents increased significantly. 4. Refeeding for 5 h returned the spermidine content of mammary glands to 'fed' values, and significantly decreased the content of spermine, although it did not reach control values. Thus changes in polyamine content of mammary gland in starved rats are clearly dissociated from changes in either RNA content or activities of polyamine-synthetic decarboxylases. 5. Starvation caused a fall in the content of spermidine in liver, with no change in spermine content. Refeeding for 5 h returned the spermidine content to 'fed' values.

Animals↗

PubMed1988

Tissue-specific effects of starvation and refeeding on the disposal of oral [1-14C]triolein in the rat during lactation and on removal of litter.

1. The effects of starvation and refeeding on the disposal of oral [14C]triolein between 14CO2 production and 14C-lipid accumulation in tissues of virgin rats, lactating rats and lactating rats with pups removed were studied. 2. Starvation (24 h) increased 14CO2 production in lactating rats and lactating rats with pups removed to values found in virgin rats. This increase was accompanied by decreases in 14C-lipid accumulation in mammary gland and pups of lactating rats and in white and brown adipose tissue of lactating rats with pups removed. 3. Short-term (2 h) refeeding ad libitum decreased 14CO2 production in lactating rats and lactating rats with pups removed, and restored the 14C-lipid accumulation in mammary glands plus pups and in white and brown adipose tissue respectively 4. Insulin deficiency induced with mannoheptulose inhibited the restoration of 14C-lipid accumulation in white adipose tissue on refeeding of lactating rats with pups removed, but did not prevent the restoration of 14C-lipid accumulation in mammary gland. 5. Changes in the activity of lipoprotein lipase in mammary gland and white adipose tissue paralleled the changes in 14C-lipid accumulation in these tissues. 6. It is concluded that 14C-lipid accumulation in mammary gland may not be affected by changes in plasma insulin concentration and that it is less sensitive to starvation than is lipogenesis or lactose synthesis. This has the advantage that the milk lipid content can still be maintained from hepatic very-low-density lipoprotein for a period after withdrawal of food. The major determinant of the disposal of oral 14C-triolein appears to be the total tissue activity of lipoprotein lipase. When this is high in mammary gland (fed lactating rats) or white adipose tissue (fed lactating rats with pups removed), less triacylglycerol is available for the muscle mass and consequently less is oxidized.

Adipose Tissue↗

PubMed2000

Response of jejunal Na+, K+-ATPase to 5-hydroxytryptamine in young and adult rats: effect of fasting and refeeding.

The present study is aimed to evaluate the effects of 5-hydroxytryptamine (5-HT) upon jejunal Na+,K+-ATPase in young (20-day-old) and adult (60-day-old) rats, and determine the effect of food intake on the response of the sodium pump to the amine. Basal Na+,K+-ATPase activity in jejunal epithelial cells from young rats was twice that in adult animals and responded to 5-HT with stimulation. In adult rats, fasting reduced by 25% basal jejunal Na+, K+-ATPase activity, whereas in young rats, no such change was observed. The sensitivity of jejunal Na+,K+-ATPase to 5-HT in young fasted rats was similar to that observed in fed animals. The effect of refeeding in young rats was a 2-fold increase in jejunal Na+, K+-ATPase activity, this being accompanied by insensitivity to 5-HT. In adult rats, refeeding was accompanied by an increase in jejunal Na+,K+-ATPase activity. It is concluded that the stimulatory effect of 5-HT upon jejunal Na+,K+-ATPase activity is a phenomenon dependent on both age and type of diet. In young rats, it is the food intake that plays an important role in development of insensitivity of Na+,K+-ATPase to stimulation by 5-HT, while in adult animals fasting or fasting followed by refeeding does not play a major role in regulating its sensitivity to the amine.

Age Factors↗

PubMed1981

The effect of restricted food intake and refeeding on the ovarian follicle population of the pre-puberal Wistar rat.

A 50 p. 100 restriction of food intake in female Wistar rats from day 21 to day 42 of life prevented ovulation and altered the size distribution and numbers of ovarian follicles. The rate of atresia of non-growing oocytes in primordial follicles was retarded resulting in more oocytes per ovary. The number of follicles initiated to grow was reduced. Semi-starved rats allowed free access to food from day 42 of life achieved the body weight of ad libitum-fed controls at 66 days of age. A delayed puberty occurred. The numbers of non-growing oocytes in primordial follicles per ovary declined but remained significantly greater than control values at 66 days of age. Refeeding increased the numbers of follicles undergoing growth but within the size distribution found in age-matched controls. Thus semi-starvation followed by refeeding rendered the ovary developmentally younger but only in terms of total oocyte numbers. The ovarian response to starvation and refeeding is discussed in relation to pituitary function and provides new information on the potential lability of the oocyte population.

Animals↗

PubMed1996

Hepatic and renal D-amino acid oxidase activities in the growing rat after ten days of protein undernutrition and refeeding.

The activity levels of hepatic and renal D-amino acid oxidase (EC 1.4.3.3), a key enzyme for D-amino acid utilization in mammals, were determined in growing rats after a 10 day period of protein undernutrition and subsequent refeeding. Reducing the protein intake for 10 days (3% casein diet) resulted in an 8% loss of the animals' mean body weight and a 50% decrease in the mean size of the liver and kidney as compared to the control animals fed on a 22% casein diet during the same period. When the undernourished rats were refed with the normal protein diet, their weight increased about four fold as compared with that of the control animals, and after a ten day period of refeeding, the lost body and tissue weights were completely recovered. As far as the specific activity of D-amino acid oxidase was concerned, a 44% reduction took place in the liver of rats subjected to protein undernutrition for 10 days. During the period of refeeding, however, the enzyme activity level increased slowly in comparison with the overall hepatic protein level, since its specific activity on day 10 was still 28% below that of the control rats. In sharp contrast, no significant change in the kidney enzyme level was observed throughout these nutritional manipulations. This study strongly suggests that the synthesis and/or catabolism of D-amino acid oxidase may depend on the dietary protein content of the liver but not on that of the kidney. This suggests that D-amino acid oxidase may possibly play distinct physiological roles in these two body organs.

Animals↗

PubMed1978

Effects of fasting and refeeding on the in vitro insulin sensitivity of rat aorta.

Rat aorta responds to refeeding after a fast in a manner similar to adopose tissue and liver by developing an enhanced capacity for lipogenesis and glycogen synthesis from glucose. The in vitro incorporation of D-U-14C-glucose into aortic triglycerides and glycogen was two- to four-fold higher in rats refed for three to five days after a three day fast than in ad libitum fed controls. Insulin significantly stimulated this incorporation only during refeeding for three days after a three-day fast. The glycogen synthesizing system appeared to be stimulated and to become sensitive to insulin earlier in the refeeding process than did the lipogenic system. The in vitro incorporation of 14C-glucose into aortic phospholipids was less affected by the nutritional state of the animal, and was not stimulated by insulin at any stage of the experiment. Possible mechanisms for the development of insulin supersensitivity and the implications for lipid accumulation in the artery wall are discussed.

Animals↗

PubMed2001

The effects of fasting and refeeding on serum parathormone and calcitonin concentrations in young and old male rats.

Although fasting and refeeding reveal the existence of age-related changes in carbohydrate and lipid metabolism, the effects of aging on mineral metabolism in refed animals are unknown. We therefore investigated hormonal regulation of calcium metabolism in young (4 months) and old (26 months) male rats fasted for 48 hours and then refed for 4 or 24 hours. Serum concentrations of total and ionized calcium and parathormone were similar in control young and old rats. Serum calcitonin level was higher, and the concentrations of albumin and inorganic phosphate and alkaline phosphatase activity were lower in fed old rats. In young fasted rats, the serum ionized and total calcium was decreased, and phosphate concentration was increased. In old rats, fasting resulted in the increase of serum parathormone level. Fasting reduced serum alkaline phosphatase activity to a similar extent in both age groups. In young rats, refeeding for 24h normalized serum calcium and phosphate levels and alkaline phosphatase activity, and decreased serum concentrations of PTH and calcitonin. In old refed rats, serum calcitonin concentration was raised by 77% compared to fed or fasted animals, whereas parathormone levels were normalized. Our results indicate that old fasted or refed rats maintain normal serum calcium concentration in a different way than young animals, possibly through the increase in serum levels of parathormone and/or calcitonin. Thus, dietary manipulations such as fasting and refeeding constitute an interesting model for the investigation of the effects of aging on the hormonal regulation of serum calcium level.

Aging↗

PubMed2002

Early refeeding after endoscopic biliary or pancreatic sphincterotomy: a randomized prospective study.

BACKGROUND AND STUDY AIMS: Patients who have undergone endoscopic sphincterotomy (ES) are usually left to fast for arbitrary reasons until they are examined on the following day. The aim of this study was to check whether this systematic fasting after ES is actually justified. PATIENTS AND METHODS: A blinded randomized prospective study, involving 146 patients, was carried out from January 1999 to September 2001. All patients undergoing biliary and/or pancreatic endoscopic sphincterotomy during this period were randomly allocated to one of two groups: group 1 patients were re-fed 4 hours after ES, and the group 2 patients were only re-fed 24 hours after the procedure. These two groups were comparable for clinical and procedural data except for stenting. RESULTS: Eight patients in group 1 (11 %) and 26 patients in group 2 (37 %) suffered from abdominal pain which resolved with analgesic drug treatment (P = 0.01). Eight patients in the first group(11 %) and five patients in the second group (7 %) had to be given major opiate analgesics (P = 0.56). Refeeding resulted in abdominal pain in five patients in group 1 and 13 in group 2 (P = 0.04). The serum amylase and lipase levels increased significantly after refeeding in group 1, but lipasemia did not increase significantly in group 2. No significant differences in post-ES complications were observed between the two groups. The mean hospital stay was significantly shorter in group 1 : 2.6 days on average, vs. 3.8 days in group 2 (P = 0.03). CONCLUSIONS: In the absence of any perforation of the digestive tract or immediate severe acute pancreatitis, early refeeding could be helpful to decrease pain and shorten the hospital stay in patients who have undergone endoscopic sphincterotomy.

Amylases↗

PubMed2005

Leptin concentrations in plasma and follicular fluid from prepubertal gilts as influenced by fasting, refeeding and insulin.

This study's aim was to examine whether fasting and refeeding would influence leptin levels in both plasma and follicular fluid from prepubertal gilts, and whether insulin affects leptin levels in fasting gilts. In experiment 1, four gilts were fasted for 72 h and then refed. Blood samples were withdrawn during normoalimentation, at the end of fasting, and for 4 h after refeeding. All samples were assayed for leptin; alternate samples were assayed for insulin, glucose and non-esterified fatty acids (NEFA). Fasting caused a decrease in leptin, glucose and insulin levels in plasma, while NEFA concentrations increased. In experiment 2, four gilts were given insulin as a bolus (0.2 IU/kg body weight) after 68 h of fasting. Blood samples were collected every 15 min around insulin administration and were assayed for leptin, insulin and glucose. This experiment shows that insulin administration increases leptin levels during fasting. In experiment 3, gilts were ovariectomized during normal alimentation (n=4), after 48 h of fasting (n=4), and after 48 h of realimentation following 48 h of fasting (n=4). Leptin levels in both plasma and follicular fluid collected after 48 h of fasting were significantly lower than those observed during normoalimentation or refeeding. In conclusion, a transient increase in insulin during fasting is effective in restoring leptin concentrations; in addition, leptin levels in follicular fluid parallel those in plasma.

Age Factors↗