The effects of starvation and refeeding on intestinal cell proliferation in the mouse

The effects of starvation and refeeding on intestinal cell proliferation were studied in four sites of the mouse intestine. Control mice were studied at different times of day in order to compensate for any circadian variations in proliferation. A circadian rhythm in crypt cell production rate was observed in all the sites of the small intestine and colon, and this rhythm appeared to be entrained to the food intake. The fractional crypt cell production rate decreased in all sites of the intestine after 24 h starvation, and remained low until 9 h after refeeding, when there was a marked increase in the crypt cell production rate of all the small intestinal sites, especially the proximal sites. There was little change in colonic crypt cell production rate until 12 h after refeeding, when there was a large increase in cell production. The crypt cell production rate of all sites then returned to control values for the remainder of the investigation. Crypt cell number decreased after refeeding and villus cell number increased, however a similar effect was observed in the control animals, nevertheless the changes in villus cell population of the refed mice occurred before any increase in crypt cell production, suggesting that cell migration from crypt to villi is not immediately dependent on cell proliferation.     

Response of plasma and tissue levels of enteroglucagon immunoreactivity to intestinal resection,lactation and hyperphagia

Elevation of plasma enteroglucagon has been described in the presence of intestinal hyperplasia in both animals and man. In order to investigate whether enteroglucagon plays a role in the stimulation of small intestinal growth, fasting plasma and small intestinal tissue levels of enteroglucagon immunoreactivity were measured in control rats and in 3 different rat models of intestinal adaptation: 5 weeks after proximal and distal small bowel resection, on the 12th day of lactation and following 5 weeks of cold acclimation induced hyperphagia. Plasma enteroglucagon levels increased significantly from the control value of 89±(SEM) 13.1 fmol/ml to 147±13.6 after proximal resection (p < 0.005) and to 207±32.6 following 5 weeks of hyperphagia (p < 0.001). During lactation ileal tissue enteroglucagon increased by 183% from 58.1±8.6 pmol/g tissue in controls to 163.9±20.4 (p < 0.001). Ileal tissue enteroglucagon levels were also elevated by 60% following proximal resection (p < 0.005) and by 91% following the hyperphagia of cold-acclimation (p < 0.005). In contrast, jejunal tissue enteroglucagon levels of cold-acclimated rats were only increased by 55% when compared to the control value of 27±2.9 pmol/g tissue (p < 0.02). These results confirm that in the rat, ileal enteroglucagon levels are significantly greater than those found in the jejunum (p < 0.005). Enteroglucagon levels were also significantly elevated in the 2 groups of rats with hyperphagia, namely the lactating and cold-acclimated groups. The data lend further support to the proposal that enteroglucagon may play a trophic role in producing intestinal growth.     

Epithelial cell proliferation and uptake of radiolabeled urogastrone in the intestinal tissues following abdominal irradiation in the mouse

We have evaluated the rate of crypt cell production and uptake of radiolabeled recombinant human urogastrone (125I-rhUG) in the intestinal tissues of the mouse at 3, 5, 7, 9, and 12 days following irradiation of the abdomen with 9 Gy. At autopsy, the animals were injected intraperitoneally with 1 microgram/g body weight of the metaphase arrest agent, vincristine sulfate, and 25 muCi of 125I-rhUG (specific activity 1.7 muCi/micrograms) to quantify the rate of crypt cell production and uptake of radiolabeled urogastrone, respectively. The results indicated that the rate of crypt cell production was increased significantly in the irradiated animals compared to the unirradiated animals and showed a peak on the 3rd and 5th postirradiation days in small intestine and colon, respectively. The uptake of 125I-rhUG was increased significantly on the 3rd postirradiation day in the intestinal tissues but showed a bimodal pattern with peaks on the 3rd and 9th postirradiation days. These results suggest that there may be a close association between epithelial cell proliferation and uptake of 125I-rhUG, particularly in the early part of recovery of intestinal mucosa following irradiation. However, these data do not discriminate whether the increased uptake of 125I-rhUG is the cause or the effect of proliferation induced by an irradiation stimulus. Further analysis also revealed that there was no relationship between crypt depth and 125I-rhUG uptake. However, crypt depth was inversely correlated with villus height in the proximal small intestine but not in the ileum. Villus height was correlated inversely with 125I-rhUG uptake in the ileum and jejunum but not the duodenum. The rate of crypt cell production was strongly correlated with crypt depth throughout the intestine and inversely correlated with villus height. This suggests that villus-to-crypt inhibitory feedback may be a primary regulator of cellular proliferation in the crypts and the association of 125I-rhUG uptake with proliferation indirectly reflects this interaction.     

Nippostrongylus brasiliensis: changes in plasma levels of gastrointestinal hormones in the infected rat

Plasma concentrations of gastrointestinal hormones were measured by radioimmunoassay in fasted rats 9 days after infection with a range of doses of Nippostrongylus brasiliensis. Values for infected rats fed ad libitum were compared with those of weight matched, pair fed, uninfected rats to control for the possible effects of dose-dependent reductions in food intake associated with infection. The plasma concentrations of some of the gastrointestinal hormones in infected rats were very different from those of their pair fed partners. The magnitude and direction of the changes varied according to the hormone being examined. Plasma concentrations of gastrin and pancreatic polypeptide were similar in pair fed and infected rats at all doses used. For the other hormones assayed, infection was associated with dose-related changes. The plasma concentrations of cholecystokinin and insulin were slightly but significantly reduced in infected rats. In contrast, secretin, enteroglucagon, and pancreatic glucagon concentrations were markedly increased. At the highest dose given (52 larvae/g body wt), the plasma levels of secretin and enteroglucagon in infected rats were elevated 9 X and 15 X, respectively. A comparison of the changes seen in N. brasiliensis-infected rats with those reported for other helminth infections revealed striking differences. The possible etiology of alterations in plasma gastrointestinal hormone concentrations and their contribution to the pathological changes seen in animals infected with helminths are discussed.     

Homologous growth hormone (GH) binding in gilthead sea bream (Sparus aurata). Effect of fasting and refeeding on hepatic GH-binding and plasma somatomedin-like immunoreactivity

Specific binding of gilthead sea bream growth hormone (sbGH) to liver membrane preparations was a time and temperature dependent process, and was saturable by increasing amounts of membrane proteins. Scatchard analysis evidenced a single class of high-affinity and lowcapacity binding sites. Ovine prolactin, recombinant tilapia prolactin, carp gonadotropin and chinook salmon gonadotropin did not compete for the¹²⁵I-sbGH binding sites, while recombinant trout GH, bovine GH and human GH displaced iodinated sbGH in a dose dependent-manner. IGF-I-like immunoreactivity was detected after acidification of plasma and removal of IGF-I binding activity. A parallel displacement to the rhIGF-1 standard was observed with extracted plasma samples. Free and total hepatic GH-binding decreased during long-term starvation (3–9 weeks), returning to control values during the refeeding period. Plasma IGF-I-like immunoreactivity showed a similar trend. To our knowledge, this is the first report that indicates a coordinated regulation of GH-binding and plasma somatomedin-like activity in a typical marine fish.     

The effects of starvation and refeeding on plasma amino acid levels in carp, Cyprinus carpio L., 1758

Plasma amino acid (AA) levels of carp, Cyprinus carpio L., 1758, were analysed after various periods of starvation as well as after 12 days of refeeding. The levels were compared to control groups, which had been previously fasted for 24 h. A positive correlation between dietary and plasma essential amino acid (EAA) concentrations was observed in all of the control groups.
The effect of starvation on the dynamics of AA concentration was different according to the period of starvation. Fasting already produced a decrease of total α-AA levels at 2 days, and these low levels were maintained until 5 and 8 days. These short periods of fasting affected the levels of EAA (especially branched-chain AA) more than those of non-essential amino acids (NEAA). The only AA that increased was Ala, which rose at 5 days of starvation, surpassing the levels of the control group. These high levels were maintained until 19 days of starvation.
A different situation was observed at 19 days, when an important increase of total α-AA levels was produced, the branched-chain AA being the most notable among EAA and Glu/Gln among NEAA. Later, at 50 days of starvation, total α-AA, EAA (except Leu and Ile) and NEAA decreased.
After 50 days of starvation, 12 days of refeeding did not modify the levels of EAA and NEAA, and their concentrations were lower than those of the control group, which presented an increase of total AA at this time. The differences observed on the changes of individual AA levels are discussed.     

Somatostatin content and binding in small intestinal mucosa from fed, fasted, and refed rabbits

The present study is an investigation of the effects of 12- to 96-hours' starvation and 96-hours' starvation plus 48-hours' refeeding on both somatostatin-like immunoreactivity (SLI) and cytosolic somatostatin binding sites in rabbit small intestinal mucosa. The SLI concentration increased after 24 h in duodenal and jejunal mucosa, but not in ileal mucosa, and reached its highest value after 96 h of fasting. The number of specific high and low-affinity somatostatin binding sites, but not their affinity, decreased with the duration of fasting in the same gut segments, refeeding of fasted animals resulted in a return to normal control values for small intestine mucosal SLI and somatostatin binding.     

A growth-stimulating activity derived from the proximal small intestine is associated with an adaptive response

Luminal nutrition is important for the maintenance of small intestinal structure and function. The equilibrium between crypt cell production and villous cell loss in the mucosal epithelium of the small intestine is altered under certain conditions such as after a small bowel resection. Immediately after resection, there is a marked increase in crypt cell proliferation giving rise to an adaptive hyperplasia in the remnant intestine and for this response luminal nutrition is a critical factor. We have previously demonstrated the presence of a growth-stimulating (GS) activity in a heat-stable acidic extract of the rat proximal intestine 24, 48, and 96 h after resection, which is coincidental with an increase in crypt cell proliferation as measured by thymidine kinase activity. Eight days after resection when the GS activity is no longer detectable, the thymidine kinase activity returns to control values. The molecular weights of the peptides associated with this GS activity are 4500 and 1500, as determined by Sephadex gel filtration. Of note is that the oral intake of food is necessary for the appearance of the GS activity postoperatively. The presence of the GS activity has also been demonstrated upon refeeding after a fast, as well as at weaning in the rat, two physiological situations known to be associated with increased proliferation in the small intestine. This GS activity in the proximal intestine first detected in the resection model may represent a general mechanism by which food controls the cell renewal pattern of the small intestine.     

Behaviour of butyrylcholinesterase in the intestinal epithelial cells of starved and refed rats.

1. The activity and the molecular characteristics of butyrylcholinesterase were studied in the epithelial cells of the following intestinal segments: duodenum, jejunum, ileum, caecum and colon of starved and refed rats. 2. After starvation, the specific activity of the enzyme is found to increase in the jejunum. The same level of activity was maintained after refeeding. No notable changes were observed in the other intestinal segments after either starvation or refeeding. 3. The behaviour of aminopeptidase, a well-characterized intestinal enzyme, is comparable to that of butyrylcholinesterase, except in the duodenum where the aminopeptidase activity is increased after refeeding. 4. In this cell type, BuChE is found only in its globular forms (G1, G2 and G4). Starvation resulted in a higher value of the sedimentation coefficient of the ileal G2 form, suggesting the existence of a complex between the enzyme and non-cholinesterase components. 5. After refeeding, the sedimentation profile was similar to that of control.     

饥饿与重摄食对河蟹肠道菌群结构的影响

研究采用16S rRNA测序研究饥饿以及重摄食的河蟹(Eriocheir sinensis)肠道菌群结构变化, 结果显示, 在饥饿胁迫下, 河蟹肠道细菌群落Alpha多样性指数下降, 重摄食后仍未改变肠道菌群多样性指数下降的趋势, 但与对照组无显著差异(P>0.05); 而在菌门组成方面, 随着饥饿时间的增加, 4个优势菌门占比呈现了相应的变化, 变形菌门、厚壁菌门以及拟杆菌门占比逐渐增加, 软壁菌门占比逐渐下降, 但在重摄食后, 4个优势菌门恢复至对照组水平; 而通过对比不同状态下差异菌群, 在科属水平下筛选出8个具有显著差异(P< 0.05)的菌群, 其中Candidatus Bacilloplasma菌属因具有较高的菌群丰度, 且对饥饿以及重摄食响应较为显著, 其菌群的特定功能值得进一步深究。研究首次报道了饥饿状态以及重摄食后河蟹肠道菌群的变化, 对于后续探究菌群的特定功能提供基础数据。     

The relationship between basal metabolic rate (BMR) and concentrations of plasma thyroid hormones in fasting cockerels

A correlation between the Basal Metabolic Rate (BMR) and the level of rT3, and occasionally between BMR and T3 or T4 was found in 12 month fasting cockerels. The birds were fasted for 48 hrs and BMR was measured eight times (before fasting, at 6, 12, 24, 30, 36, and 48 hrs of fasting, and 4 hours after fasting). Blood samples for plasma collection were taken immediately after measuring the BMR. During starvation a decrease in BMR was observed. After refeeding BMR returned to the starting level. The decrease in BMR was accompanied by an increase in rT3 and T4 plasma levels. Between BMR and levels of T4 and rT3 negative coefficients of correlation were observed (r = -0.20 and r = -0.42, respectively). Contrary to this, the T3 level declined and was correlated with BMR (r = 0.62). After refeeding, the T3 level rapidly increased against the control value. Moreover, a high coefficient of correlation (r = -0.39) was found between the level of T3 and rT3. The data show that the reduction in plasma T3 level and increase in the rT3 one during starvation may be due to inhibition of deiodination of T4 to T3, since rT3 is a competitive inhibitor of this reaction. The presented results support the suggestion that in birds T3 is the metabolically active thyroid hormone, and rT3 antagonizes this effect.     

Cell kinetics in the mouse small intestine during immediate postnatal life

The cell proliferation kinetics in the small intestine of newborn Balb/c mice were studied, from day 1 through to day 21 after birth. The size of the functional compartment and the proliferation compartment was determined as well as the cell production rate in the crypt using the micro-dissection technique combined with metaphase arrest method. The effect of weaning on cell proliferation was studied. The results suggest that: (1)There is continuous increase in cell proliferation and in the size of the functional and proliferative compartment over the 21 days. (2) The cell proliferation proceeds at a slower rate than in adult animals. (3) There is a sharp increase in cell production rate during the third week of postnatal life. (4) The cell proliferation was faster in conventionally weaned litters than the non-weaned group. (5) The intestinal mucosa in newborn mice is not in a steady-state conditions as in adults; cell production rate exceeds cell loss.     

FGFR3 contributes to intestinal crypt cell growth arrest

Fibroblast growth factors (FGFs) are important regulators of the dynamic development and turnover of tissues. Among FGF receptors, FGFR3 expression is confined in the intestinal crypts. We examined FGFR3-deficient mice and saw increased intestinal crypt depth but no change in villae length or in the distribution of differentiated intestinal cells, suggesting that the impact of lack of FGFR3 was limited to the progenitor cell compartment. Accordingly, enhancement of intestinal crypt proliferation was observed in FGFR3 mutant mice and interestingly, upon anti-FGFR3 antibody administration in wild type mice. Moreover, injection of FGF18, a ligand of FGFR3, in wild type mice resulted in decreased cell proliferation within the intestinal crypts. In addition, we found that ERK level of activation was increased in FGFR3-deficient intestinal epithelium. In vitro studies showed that ERK, AKT and activation was regulated by FGFs and that ERK level of activation was inversely correlated to FGFR3 level of expression in the intestinal crypt cells. Furthermore, effects of FGF18 on ERK and AKT activation paralleled FGFR3 effects on these intracellular targets. Our data indicate that FGF18 and FGFR3 are involved, possibly as partners, in the control of intestinal precursor cell proliferation.     

Effects of starvation and refeeding on gonadotropin and thyrotropin subunit mRNAs in male Japanese quail

The contents of mRNAs encoding LH beta-, FSH beta-, TSH beta- and common alpha-subunit precursor molecules were measured in food-deprived and subsequently re-fed male Japanese quail. Pituitary LH beta, FSH beta and common alpha mRNA levels were decreased by starvation, and increased to the control levels by re-feeding. The rates of decreases of LH beta and common alpha mRNA levels were greater the corresponding rate for FSH beta levels. Pituitary TSH beta mRNA levels were not decreased by starvation, but increased transitorily by re-feeding. Plasma LH and triiodothyronine levels were decreased by starvation, and then increased to control levels by re-feeding, while plasma FSH and thyroxine levels did not show significant changes. Plasma LH and FSH levels showed positive correlations with pituitary common alpha and FSH beta mRNA levels, respectively, while plasma thyroxine levels showed a negative correlation with TSH beta mRNA levels. Hepatic weight was decreased slightly but significantly by starvation, and then showed a remarkable rebound after re-feeding was started. These results suggest that LH synthesis and secretion are more sensitive to starvation than FSH synthesis and secretion in Japanese quail, and that LH production recovered to initial levels within several days when birds were fully fed. Also, there is a possibility that the synthesis of TSH is accelerated transitorily by re-feeding. Furthermore, these results showed that there are different relationships between the plasma levels of LH, FSH, and TSH and the various hormone subunit mRNA levels. The remarkable change in hepatic weight leads us to assume that hepatic thyroid hormone metabolism is affected by starvation and re-feeding.     

Temporal and spatial dynamics underlying capacitative calcium entry in human colonic smooth muscle

Angiotensin converting enzyme (ACE) has been shown to be involved in regulation of apoptosis in nonintestinal tissues. This study examined the role of ACE in the modulation of intestinal adaptation utilizing ACE knockout mice (ACE-/-). A 60% small bowel resection (SBR) was used, since this model results in a significant increase in intestinal epithelial cell (EC) apoptosis as well as proliferation. Baseline villus height, crypt depth, and intestinal EC proliferation were higher, and EC apoptosis rates were lower in ACE-/- compared with ACE+/+ mice. After SBR, EC apoptosis rates remained significantly lower in ACE-/- compared with ACE+/+ mice. Furthermore, villus height and crypt depth after SBR continued to be higher in ACE-/- mice. The finding of a lower bax-to-bcl-2 protein ratio in ACE-/- mice may account for reduced EC apoptotic rates after SBR in ACE-/- compared with ACE+/+ mice. The baseline higher rate of EC proliferation in ACE-/- compared with ACE+/+ mice may be due to an increase in the expression of several EC growth factor receptors. In conclusion, ACE appears to have an important role in the modulation of intestinal EC apoptosis and proliferation and suggests that the presence of ACE in the intestinal epithelium has a critical role in guiding epithelial cell adaptive response.     

A qualitative comparison of canine plasma gastroenteropancreatic hormone responses to bombesin and the porcine gastrin-releasing peptide (GRP)

The effect on plasma gastroenteropancreatic hormone levels on infusing the porcine gastrin-releasing peptide and bombesin into dogs demonstrated no qualitative difference in the spectrum of activity of the two peptides. Sustained elevations in plasma immunoreactive gastrin, pancreatic polypeptide, enteroglucagon, gastric inhibitory polypeptide, pancreatic glucagon and transient elevations in plasma insulin were seen during infusions of both peptides. The similar spectrum of activities and the structural homology between the two peptides suggests that the porcine gastrin releasing peptide is the porcine counterpart of the amphibian peptide bombesin.     

The thyroid hormone receptor-alpha (TRalpha) gene encoding TRalpha1 controls deoxyribonucleic acid damage-induced tissue repair

The thyroid hormone (TH) controls, via its nuclear receptor, TH receptor-alpha1 (TRalpha1), intestinal crypt cell proliferation in the mouse. In order to understand whether this receptor also plays a role in intestinal regeneration after DNA damage, we applied a protocol of gamma-ray irradiation and monitored cell proliferation and apoptosis at several time points. In wild-type mice, the dose of 8 Gy induced cell cycle arrest and apoptosis in intestinal crypts a few hours after irradiation. This phenomenon reverted 48 h after irradiation. TRalpha(0/0) mutant mice displayed a constant low level of proliferating cells and a high apoptosis rate during the period of study. At the molecular level, in TRalpha(0/0) animals we observed a delay in the p53 phosphorylation induced by DNA damage. In our search for the expression of the protein kinases responsible for p53 phosphorylation upon irradiation, we have focused on DNA-dependent protein kinase catalytic subunit (DNA-PKcs). The number of cells expressing DNA-PKcs in crypts remained high 48 h after irradiation, specifically in TRalpha mutants. Altogether, in TRalpha(0/0) animals the rate of apoptosis in crypt cells remained high, apparently due to an elevated number of cells still presenting DNA damage. In conclusion, the TRalpha gene plays a role in crypt cell homeostasis by regulating the rate of cell renewal and apoptosis induced by DNA damage.     

Effects of starvation on gonadotropin and thyrotropin subunit mRNA levels and plasma hormone levels in the male Japanese quail (Coturnix coturnix japonica)

Contents of mRNAs encoding LHbeta-, FSHbeta-, TSHbeta- and common a-subunit precursor molecules were measured in male Japanese quail deprived of food for three days. Plasma LH, FSH, thyroxine and triiodothyronine levels were also measured in the same birds. Plasma LH levels declined during the period of food deprivation. Levels in starved birds were not different from those in control birds after one day of starvation but were significantly lower after three days. Plasma FSH levels showed a similar decline, although the changes were not significant. Plasma thyroxine levels did not decrease during starvation, whilst plasma triiodothyronine levels decreased drastically and significantly soon after the start of starvation. All the hormone subunit mRNA contents in starved birds also decreased, with differences from control birds significant 3 days after the start of starvation. Plasma FSH levels showed a strong positive correlation with pituitary FSHbeta mRNA levels, while plasma LH levels had a strong positive correlation with common a mRNA levels and practically no correlation or even a negative correlation with LHbeta mRNA levels. These results suggest that starvation suppresses not only gonadotropin and thyrotropin secretion but also their synthesis in the pituitary gland. Furthermore, these results showed that FSH and LH have different synthesis and secretion dynamics in the Japanese quail. Contradicting results with TSHbeta mRNA and thyroid hormones lead us to assume that starvation affects thyroid hormone metabolism in peripheral tissue, presumably in the liver.