Diet restriction increases apoptosis in the gut of aging rats

Nutritional strategies to reduce intestinal cell apoptosis by alleviating oxidative stress

The gut barrier is the first line of defense against harmful substances and pathogens in the intestinal tract. The balance of proliferation and apoptosis of intestinal epithelial cells (IECs) is crucial for maintaining the integrity of the intestinal mucosa and its function. However, oxidative stress and inflammation can cause DNA damage and abnormal apoptosis of the IECs, leading to the disruption of the intestinal epithelial barrier. This, in turn, can directly or indirectly cause various acute and chronic intestinal diseases. In recent years, there has been a growing understanding of the vital role of dietary ingredients in gut health. Studies have shown that certain amino acids, fibers, vitamins, and polyphenols in the diet can protect IECs from excessive apoptosis caused by oxidative stress, and limit intestinal inflammation. This review aims to describe the molecular mechanism of apoptosis and its relationship with intestinal function, and to discuss the modulation of IECs' physiological function, the intestinal epithelial barrier, and gut health by various nutrients. The findings of this review may provide a theoretical basis for the use of nutritional interventions in clinical intestinal disease research and animal production, ultimately leading to improved human and animal intestinal health.

Calorie restriction prevents age-related changes in the intestinal microbiota

The effect of calorie restriction (CR) on the microbiome, fecal metabolome, and colon transcriptome of adult and old male mice was compared. Life-long CR increased microbial diversity and the Bacteroidetes/Firmicutes ratio and prevented the age-related changes in the microbiota, shifting it to a younger microbial and fecal metabolite profile in both C57BL/6JN and B6D2F1 mice. Old mice fed CR were enriched in the Rikenellaceae, S24-7 and Bacteroides families. The changes in the microbiome that occur with age and CR were initiated in the cecum and further modified in the colon. Short-term CR in adult mice had a minor effect on the microbiome but a major effect on the transcriptome of the colon mucosa. These data suggest that CR has a major impact on the physiological status of the gastrointestinal system, maintaining it in a more youthful state, which in turn could result in a more diverse and youthful microbiome.

Complementary intestinal mucosa and microbiota responses to caloric restriction

The intestine is key for nutrient absorption and for interactions between the microbiota and its host. Therefore, the intestinal response to caloric restriction (CR) is thought to be more complex than that of any other organ. Submitting mice to 25% CR during 14 days induced a polarization of duodenum mucosa cell gene expression characterised by upregulation, and downregulation of the metabolic and immune/inflammatory pathways, respectively. The HNF, PPAR, STAT, and IRF families of transcription factors, particularly the Pparα and Isgf3 genes, were identified as potentially critical players in these processes. The impact of CR on metabolic genes in intestinal mucosa was mimicked by inhibition of the mTOR pathway. Furthermore, multiple duodenum and faecal metabolites were altered in CR mice. These changes were dependent on microbiota and their magnitude corresponded to microbial density. Further experiments using mice with depleted gut bacteria and CR-specific microbiota transfer showed that the gene expression polarization observed in the mucosa of CR mice is independent of the microbiota and its metabolites. The holistic interdisciplinary approach that we applied allowed us to characterize various regulatory aspects of the host and microbiota response to CR.

Pre-adult famine exposure and subsequent colorectal cancer risk in women

Background

Nutritional deprivation during growth and development may contribute to colorectal cancer (CRC) risk in later life.

Methods

We studied 7906 women who were aged 0-21 years during the 1944-45 Dutch famine, who enrolled in the Prospect-EPIC study between 1993 and 1997. We used Cox proportional hazard analyses to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for colorectal (proximal, distal and rectal) cancer risk across self-reported famine exposure and exposure-age categories, while adjusting for potential confounders.

Results

During a median of 17.3 years of follow-up, 245 CRC cases occurred. Moderately and severely famine-exposed women showed a respective 24% and 44% higher CRC risk compared with women who reported no exposure [HR moderate 1.24 (95% CI: 0.93-1.64); HR severe 1.44 (1.03-2.03); P trend 0.027]. This relation attenuated when adjusted for potential confounders [adjusted HR moderate 1.15 (0.87-1.53); HR severe 1.35 (0.96-1.90); P trend 0.091]. Stratified results suggested that severe famine exposure between 10 and 17 years of age was particularly related to CRC risk[adjusted HR moderate 1.39 (0.91-2.11); HR severe 1.76 (1.10-2.83); P trend 0.019; P interaction(famine*10-17yrs) 0.096]. Overall, we found no differences in famine effects across CRC subsites, but age-at-exposure stratified results suggested an increased risk for proximal CRC in those aged 10-17 years during exposure to the famine [adjusted HR moderate 2.14 (1.06-4.32), HR severe 2.96 (1.35-6.46); P trend 0.005]. Overall and within age-at-exposure categories, tests for subsite specific heterogeneity in famine effects were not significant.

Conclusions

Our findings suggest that severe exposure to a short period of caloric restriction in pre-adult women may relate to CRC risk decades later.

Green Tea Induced Cellular Proliferation and the Expression of Transforming Growth Factor-β1 in the Jejunal Mucosa of Fasting Rats

OBJECTIVE

The aim of this study was to understand whether or not the protective effect of green tea after fasting-induced damage in the jejunal mucosa of rat is dependent on cell proliferation and the stimulation of specific growth factors.

MATERIALS AND METHODS

Sixty adult male Wistar rats were used in this study. The animals were divided randomly into 5 groups, with 12 in each group (G1-5). The animals in G1 (control group) were fed a rat chow diet and water ad libitum. The animals in G2 (fasting group) were fasted for 3 days. The animals in the G3, G4, and G5 groups were fasted for 3 days as G2, but were given water (G3), green tea (G4), or a vitamin E (G5) solution, respectively, for another 7 days. The animals were euthanized, and the jejunum was removed and processed for histological and immunohistochemical analysis.

RESULTS

Compared to the G3 group, the jejunal mucosa of G4 rats showed a 70.6% higher level (p < 0.001) of expression of proliferating cell nuclear antigen and 98% higher level (p = 0.0001) of the expression of transforming growth factor-β1 (TGF-β1), whereas the level of fibroblast growth factor-1 (FGF-1) and insulin-like growth factor-1 (IGF-1) expression was 22 and 11% lower, respectively, in G4 animals as compared to G3 rats. These differences in the expression of FGF-1 and IGF-1 in G4 animals were not statistically significant.

CONCLUSION

In this study, green tea repaired the fasting-induced damage in the jejunal mucosa of rats, mainly by inducing a significant expression of TGF-β1 in the jejunal mucosa.

Effects of a grape-supplemented diet on proliferation and Wnt signaling in the colonic mucosa are greatest for those over age 50 and with high arginine consumption

A diet rich in fruits and vegetables, and a grape-derived compound, resveratrol, have been linked to a reduced incidence of colon cancer. In vitro and in vivo, resveratrol suppresses Wnt signaling, a pathway constitutively activated in over 85 % of colon cancers.

Thirty participants were placed on a low resveratrol diet and subsequently allocated to one of three groups ingesting 1/3-to-1 lb (0.15–0.45 kg) of grapes per day for 2 weeks. Dietary information was collected via 24-h recall. Colon biopsies for biomarker analysis were obtained pre- and post-grape and evaluated for the expression of Wnt pathway target genes and for markers of proliferation by RT-PCR and immunohistochemistry.

Participants lost an average of 2 · 6 lb (1.2 kg, p = 0 · 0018) during the period of grape ingestion. The expression of CyclinD1 (p < 0 · 01), AXIN2, CD133 (p = 0 · 02) and Ki67 (p = 0 · 002) were all reduced after grape ingestion. Individuals over 50 years of age and those with high dietary arginine consumption had increased basal expression of CyclinD1, AXIN2, cMYC and CD133 (p value range 0 · 04 to <0 · 001) that, following grape ingestion, were reduced to levels seen in younger participants.

The reduction in Wnt signaling and mucosal proliferation seen following short-term ingestion of 1/3–1 lb (0.15–0.45 kg) of grapes per day may reduce the risk of mutational events that can facilitate colon carcinogenesis. The potential benefit is most marked for high-risk older individuals and individuals whose diet is high in arginine intake. Dietary grape supplementation may play a role in colon cancer prevention for high-risk individuals.

Nutrition, sirtuins and aging

Beyond our inherited genetic make-up environmental factors are central for health and disease and finally determine our life span. Amongst the environmental factors nutrition plays a prominent role in affecting a variety of degenerative processes that are linked to aging. The exponential increase of non-insulin-dependent diabetes mellitus in industrialized nations as a consequence of a long-lasting caloric supernutrition is an expression of this environmental challenge that also affects aging processes. The most consistent effects along the environmental factors that slow down aging - from simple organisms to rodents and primates - have been observed for caloric restriction. In the yeast Saccharomyces cerevisiae, the fruit fly Drosophila melanogaster and the nematode Caenorhabditis elegans, sirtuins (silencing information regulators) have been identified to mediate as "molecular sensors" the effects of caloric restriction on aging processes. Sirtuins are NAD(+)-dependent deacetylases that are activated when e.g. cell energy status is low and the NAD(+) over NADH ratio is high. As a consequence transcription rates of a variety of genes including that of the apoptosis inducing p(53) gene are reduced. Moreover, in C. elegans, sirtuins were shown to interact with proteins of the insulin/IGF-1 signaling cascade of which several members are known to extend life span of the nematodes when mutated. Downstream targets of this pathway include genes that encode antioxidative enzymes such as Superoxide dismutase (SOD) whose transcription is activated when receptor activation by insulin/IGF is low or when sirtuins are active and the ability of cells to resist oxidative damage appears to determine their life span. Amongst dietary factors that activate sirtuins are certain polyphenols such as quercetin and resveratrol. Whereas their ability to affect life span has been demonstrated in simple organisms, their efficacy in mammals awaits proof of principle.

Apoptotic genes are differentially expressed in aged gingival tissue

Cellular and molecular changes of the periodontium associated with a higher prevalence of oral diseases (e.g., chronic periodontitis) in aged populations have received little attention. Since impaired apoptosis during aging appears to be related to chronic inflammatory disorders, we hypothesized that the expression of genes associated with apoptotic processes are altered in aged healthy and periodontitis-affected gingival tissue. Ontology analysis of 88 genes related to apoptotic pathways was performed in gingival biopsies of healthy and periodontitis sites from young, adult, and aged non-human primates (Macaca mulatta), using the GeneChip® Rhesus Macaque Genome Array. Lower expression of anti-apoptotic and higher expression of pro-apoptotic genes were associated with healthy gingival tissue from young compared with aged animals. Few differences in gene expression were observed in healthy gingival tissue between adult and aged animals. Comparison between healthy and periodontitis gingival tissues showed that the up- or down-regulated apoptotic genes in diseased gingival tissue are different in adults compared with aged animals. These results suggest that apoptotic events normally occurring in gingival tissues could be reduced in aging,and unique aspects of apoptotic pathways are potentially involved in the pathophysiology of periodontal disease in adult vs. aged gingival tissues.

Effect of aging on gastric mucosal defense mechanisms: ROS, apoptosis, angiogenesis, and sensory neurons

Aging changes in the stomach lead to a decreased capacity for tissue repair in response to gastric acid. The aim of this study was to determine the mechanism associated with the increased susceptibility to injury of aging mucosa including reactive oxygen species (5), apoptosis, angiogenesis, and sensory neuron activity. Fischer 344 rats at four different ages (6, 31, 74 wk, and 2 yr of age) were studied. The connective tissue indicators [salt-soluble collagen and sulfated glycosaminoglycan (sGAG)], lipid hydroperoxide (LPO), myeloperoxidase (MPO), and hexosamine were assessed. We also evaluated the expression of early growth response-1 (Egr-1), phosphatase and tension homologue deleted on chromosome 10 (PTEN), caspase-9 (index of apoptosis), VEGF (index of angiogenesis), calcitonin gene-related peptide (CGRP, index of sensory neurons), and neuronal nitric oxide synthase (nNOS). The histological connective tissue area in the lower part of rat gastric mucosa increased with aging, with increase of salt-soluble collagen and sGAG. LPO and MPO in old rats were significantly greater than in the young rats, whereas hexosamine was significantly reduced. The old gastric mucosa had increased expression of Egr-1, PTEN, and caspase-9, whereas the VEGF, CGRP, and nNOS expression were significantly reduced. These results indicate that the lower part of rat gastric mucosa was found to be replaced by connective tissue with accumulation of oxidative products with aging. In addition, impairment of apoptosis, angiogenesis, and sensory neuron activity via the activation of Egr-1 and PTEN might increase the susceptibility of gastric mucosa to injury during aging.

Caloric restriction: from soup to nuts

Caloric restriction (CR), reduced protein, methionine, or tryptophan diets; and reduced insulin and/or IGFI intracellular signaling can extend mean and/or maximum lifespan and delay deleterious age-related physiological changes in animals. Mice and flies can shift readily between the control and CR physiological states, even at older ages. Many health benefits are induced by even brief periods of CR in flies, rodents, monkeys, and humans. In humans and nonhuman primates, CR produces most of the physiologic, hematologic, hormonal, and biochemical changes it produces in other animals. In primates, CR provides protection from type 2 diabetes, cardiovascular and cerebral vascular diseases, immunological decline, malignancy, hepatotoxicity, liver fibrosis and failure, sarcopenia, inflammation, and DNA damage. It also enhances muscle mitochondrial biogenesis, affords neuroprotection; and extends mean and maximum lifespan. CR rapidly induces antineoplastic effects in mice. Most claims of lifespan extension in rodents by drugs or nutrients are confounded by CR effects. Transcription factors and co-activators involved in the regulation of mitochondrial biogenesis and energy metabolism, including SirT1, PGC-1alpha, AMPK and TOR may be involved in the lifespan effects of CR. Paradoxically, low body weight in middle aged and elderly humans is associated with increased mortality. Thus, enhancement of human longevity may require pharmaceutical interventions.

Is stomach spontaneously ageing? Pathophysiology of the ageing stomach

During ageing, histological and physiological modifications occur in the stomach leading to a confirmed state of gastric frailty defined by a decreased capacity of tissue repairing after mucosa gastric aggression. The process of intrinsic gastric ageing may play a role in inducing abnormalities of gastric epithelial proliferation against injury but, most of the time, pathophysiological modifications observed in older people are the consequences of chronic insults, such as chronic Helicobacter pylori infection, polymedication, especially Proton-pump inhibitors (PPI) and Non-steroidal Anti-inflammatory Drugs (NSAID), and co morbidities. One of the major clinical consequences of the gastric frailty is the higher vulnerability to the occurrence of peptic ulcer disease during ageing. In this review recent data on gastric changes during ageing, focussing especially on histological modifications and motility disorders are summarized.

Second hit post burn increased proximal gut mucosa epithelial cells damage

Secondary infections after burn are common and are a major contributor to morbidity and mortality. We previously showed that burn disrupted proximal gut mucosal homeostasis through increased epithelial cell apoptosis. In the present study, we sought to determine whether proximal gut mucosal disruption is additively affected by secondary endotoxemia after a severe burn. C57BL/6 mice received 30% total body surface area full-thickness scald burns and were randomized to receive saline or LPS 1 mg/kg body weight given intraperitoneally 72 h after burn. Proximal small bowel was harvested 12 h after LPS injection. Mucosal height and epithelial cell number were assessed on hematoxylin-eosin sections, intestinal epithelial cell apoptosis was identified by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling, and cell proliferation by immunohistochemical staining for proliferating cell nuclear antigen. Results showed that proximal gut mucosa impairment occurred 12 h after injury, including significantly decreased proximal gut wet weight, gut mucosal height, and epithelial cell number associated with increased proximal gut epithelial apoptosis (P < 0.05). This impairment diminished 72 h after burn. Second-hit endotoxemia caused additional proximal gut mucosa damage with decreased proximal gut weight, cell number, and mucosal height (P < 0.05) and significantly increased small intestinal epithelial apoptosis and mucosal atrophy, even after the first event, indicating a second detrimental effect of endotoxemia after the initial injury.

Conserved and tissue-specific genic and physiologic responses to caloric restriction and altered IGFI signaling in mitotic and postmitotic tissues

Caloric restriction (CR), the consumption of fewer calories without malnutrition, and reduced insulin and/or IGFI receptor signaling delay many age-related physiological changes and extend the lifespan of many model organisms. Here, we present and review microarray and biochemical studies indicating that the potent anticancer effects of CR and disrupted insulin/IGFI receptor signaling evolved as a byproduct of the role of many mitotic tissues as reservoirs of metabolic energy. We argue that the longevity effects of CR are derived from repeated cycles of apoptosis and autophagic cell death in mitotically competent tissues and protein turnover and cellular repair in postmitotic tissues. We review studies showing that CR initiated late in life can rapidly induce many of the benefits of lifelong CR, including its anticancer effects. We also discuss evidence from liver and heart indicating that many benefits of lifelong CR are recapitulated in mitotic and postmitotic tissues when CR is initiated late in life.

Chronic low intake of protein or vitamins increases the intestinal epithelial cell apoptosis in Wistar/NIN rats

OBJECTIVE

Malnutrition decreases antioxidant defense and increases oxidative stress in the intestine. We studied the effects of long-term restriction of food, protein, and vitamins on intestinal epithelial cell (IEC) apoptosis and the underlying mechanisms.

METHODS

Weanling, Wistar/NIN male rats were fed ad libitum with a control diet, 75% protein-restricted diet, or 50% vitamin-restricted diet for 20 wk. The food-restricted group received 50% of the diet consumed by control rats. IEC apoptosis was monitored by morphometry, Annexin V binding, M30 CytoDeath assay, and DNA fragmentation. Structural and functional integrity of the villus were assessed by the ratio of villus height to crypt depth, and alkaline phosphatase and lys, ala-dipeptidyl aminopeptidase activities, respectively. Oxidative stress parameters, caspase-3 activity, and expression of Bcl-2 and Bax were determined to assess the probable mechanisms of altered apoptosis.

RESULTS

Protein and vitamin restrictions but not food restriction significantly increased IEC apoptosis and only vitamin restriction altered structural and functional integrity of villi. Increased levels of protein carbonyls, thiobarbituric acid reactive substances, and caspase-3 activity along with decreased glutathione levels and Bcl-2 expression were observed in IECs of these rats, whereas food restriction did not affect these parameters.

CONCLUSIONS

Protein restriction increased only IEC apoptosis, whereas vitamin restriction also affected the structure and function of villi. Modulation of the pathway mediated by mitochondria through increased oxidative stress appears to be the probable mechanism underlying this effect.

Long-lived αMUPA transgenic mice show reduced SOD2 expression, enhanced apoptosis and reduced susceptibility to the carcinogen dimethylhydrazine

Calorie restriction (CR) extends the life span of various species through mechanisms that are as yet unclear. Recently, we have reported that mitochondrion-mediated apoptosis was enhanced in alphaMUPA transgenic mice that spontaneously eat less and live longer compared with their wild-type (WT) control mice. To understand the molecular mechanisms underlying the increased apoptosis, we compared alphaMUPA and WT mice for parameters associated with SOD2 (MnSOD), a mitochondrial antioxidant enzyme that converts superoxide radicals into H(2)O(2) and is also known to inhibit apoptosis. The SOD2-related parameters included the levels of SOD2 mRNA, immunoreactivity and enzymatic activity in the liver, lipid oxidation and aconitase activity in isolated liver mitochondria, and the sensitivity of the mice to paraquat, an agent that elicits oxidative stress. In addition, we compared the mice for the levels of SOD2 mRNA after treatment with bacterial lipopolysaccharides (LPS), and for the DNA binding activity of NFkappaB as a marker for the inflammatory state. We extended SOD2 determination to the colon, where we also examined the formation of pre-neoplastic aberrant crypt foci (ACF) following treatment with dimethylhydrazine (DMH), a colonic organotypic carcinogen. Overall, alphaMUPA mice showed reduced basal levels of SOD2 gene expression and activity concomitantly with reduced lipid oxidation, increased aconitase activity and enhanced paraquat sensitivity, while maintaining the capacity to produce high levels of SOD2 in response to the inflammatory stimulus. alphaMUPA mice also showed increased resistance to DMH-induced pre-neoplasia. Collectively, these data are consistent with a model, in which an optimal fine-tuning of SOD2 throughout a long-term regimen of reduced eating could contribute to longevity, at least in the alphaMUPA mice.

Iron dysregulation combined with aging prevents sepsis-induced apoptosis

BACKGROUND

Sepsis, iron loading, and aging cause independent increases in gut epithelial and splenic apoptosis. It is unknown how their combination will affect apoptosis and systemic cytokine levels.

MATERIALS AND METHODS

Hfe-/- mice (a murine homologue of hemochromatosis) abnormally accumulate iron in their tissues. Aged (24-26 months) or mature (16-18 months) Hfe-/- mice and wild type (WT) littermates were subjected to cecal ligation and puncture (CLP) or sham laparotomy. Intestine, spleen, and blood were harvested 24 h later and assessed for apoptosis and cytokine levels.

RESULTS

Gut epithelial and splenic apoptosis were low in both aged septic and sham Hfe-/- mice, regardless of the amount of iron in their diet. Mature septic WT mice had increased apoptosis compared to age-matched sham WT mice. Mature septic Hfe-/- mice had similar levels of intestinal cell death to age-matched septic WT mice but higher levels of splenic apoptosis. Apoptosis was significantly lower in septic aged Hfe-/- mice than septic mature Hfe-/- animals. Interleukin-6 was elevated in septic aged Hfe-/- mice compared to sham mice.

CONCLUSIONS

Although sepsis, chronic iron dysregulation, and aging each increase gut and splenic apoptosis, their combination yields cell death levels similar to sham animals despite the fact that aged Hfe-/- mice are able to mount an inflammatory response following CLP and mature Hfe-/- mice have elevated sepsis-induced apoptosis. Combining sepsis with two risk factors that ordinarily increase cell death and increase mortality in CLP yields an apoptotic response that could not have been predicted based upon each element in isolation.

The effect of hepatocyte growth factor on gut mucosal apoptosis and proliferation, and cellular mediators after severe trauma

BACKGROUND

A severe burn injury is associated with an impairment of gut mucosal integrity and function, which is due to increases in small-bowel epithelial cell apoptosis and decreases in cell proliferation. Hepatocyte growth factor (HGF) was shown to improve regeneration in the liver, mesentery, and skin. The purpose of this study was to determine whether HGF can improve small-bowel homeostasis after injury and the cellular mechanisms by which these changes occur.

METHODS

Rats were pair-fed, underwent thermal trauma, and received saline (0.9% NaCl; n = 28) or HGF (200 microg/kg iv every 12 hours, n = 28). Small intestine and serum were taken at 1, 2, 5, and 7 days after injury. Measures were mucosal apoptosis, proliferation, villous morphology, and apoptotic and proliferative mediators, such as caspase-3 and caspase-7, Fas and Fas-ligand, Bcl-2, and Bax. In addition, serum cytokines were determined.

RESULTS

Gut epithelial cell apoptosis was increased in the saline and HGF groups after the thermal injury. Despite an increase in serum tumor necrosis factor-alpha and interleukin-1beta, HGF did not affect small-bowel cell apoptosis, but it improved proliferation at days 1 and 2 after injury, which was associated with increased villous height and cell per villous, compared with saline controls, P < .05. Increased mucosal cell proliferation was associated with increased Bcl-2 in the HGF group, P < .05. HGF had no effect on apoptotic mediators, such as Fas, Fas-L, or caspase-3 and caspase-7.

CONCLUSIONS

HGF improves small-bowel morphology after a severe burn by increasing mucosal Bcl-2 and, concomitantly, small-bowel epithelial cell proliferation.

Effects of vitamin restriction and supplementation on rat intestinal epithelial cell apoptosis

Diet influences intestinal growth and function and vitamins modulate intestinal cell turnover. We have assessed the effects of chronic, moderate (50% of control) vitamin restriction and supplementation on intestinal epithelial cell (IEC) apoptosis and the relevance of this to alterations in tissue oxidative stress and antioxidant status. Feeding a vitamin-restricted diet to male, weanling WNIN rats for 20 weeks significantly increased IEC apoptosis, but only in the villi region, as evident from increased annexin V staining, M30 positivity, histological observations, DNA ladder formation, and reduced expression of Bcl-2. This was associated with elevated levels of lipid peroxides and protein carbonyls in the intestinal mucosa despite the increased activities of superoxide dismutase, catalase, and glutathione peroxidase. Consistent with the increased oxidative stress and apoptosis, structural and functional integrity of the villi were compromised as evident from the lowered ratio of villus height:crypt depth and the decreased activities of the membrane marker enzymes alkaline phosphatase and Lys-Ala dipeptidyl aminopeptidase. These changes were reversed by supplementation with a vitamin mixture or vitamin E alone, whereas riboflavin or folic acid supplementation reduced the apoptotic rates, but only partially. Further, oxidative stress was the least in vitamin E- or vitamin mixture-supplemented rats and correlated well with their IEC apoptotic rates. Increased tissue oxidative stress seems to mediate the vitamin-restriction-induced apoptosis of the IECs in rats.

Age disproportionately increases sepsis-induced apoptosis in the spleen and gut epithelium

Both aging and sepsis independently increase splenic and gut epithelial apoptosis. Sepsis-induced apoptosis in either cell type is also associated with increased mortality in young mice. We sought to determine whether age alters sepsis-induced splenic and gut epithelial cell death. Young (2 months) and aged (22 months) male ND4 mice were subjected to either single-puncture cecal ligation and puncture (CLP) with a 23-gauge needle or sham laparotomy. Apoptosis was assessed 24 hours later in the spleen and gut epithelium by active caspase 3 and hematoxylin and eosin staining. Aged septic mice had increased splenic apoptosis compared with either young septic animals or aged sham animals (15 vs. 7 vs. 5 apoptotic cells/high-powered field, P < 0.05). Similarly, aged septic animals had an elevation in gut epithelial cell death compared with either young septic or aged sham mice (33 vs. 16 vs. 6 apoptotic cells/100 contiguous crypts, P < 0.05). Elevated intestinal cell death was not associated with changes in either gut proliferation or cell division. To verify that the increase in splenic apoptosis seen in septic aged animals was not strain specific, double-puncture CLP with a 25-gauge needle or sham laparotomy was performed on young (4 months) or aged (24 months) C57BL/6 male mice. Similar to results seen in outbred animals, aged septic animals in this inbred strain had increased splenic apoptosis compared with either young septic animals or aged sham animals (23 vs. 7 vs. 4 apoptotic cells/ high powered field, P < 0.05). These results indicate that although infection and aging each independently cause an increase in splenic and gut epithelial apoptosis, their combination leads to a disproportionate increase in cell death in these rapidly dividing cell populations,and potentially plays a role in the marked increase in mortality seen with aging in sepsis.

Mucosal adaptation to enteral nutrients is dependent on the physiologic actions of glucagon-like peptide-2 in mice

BACKGROUND & AIMS

Our understanding of the intestinotropic actions of glucagon-like peptide-2 (GLP-2)(1-33) is based on pharmacologic studies involving exogenous administration. However, the physiologic role of GLP-2 in mucosal growth and adaptation to nutritional stimulation remains poorly understood.

METHODS

The properties of GLP-2(3-33), a GLP-2(1-33) metabolite, were determined in baby-hamster kidney cells transfected with the mouse GLP-2 receptor complementary DNA and in isolated murine intestinal muscle strips. To investigate the role of endogenous GLP-2(1-33) in gut adaptation, GLP-2(3-33) was administered to mice that were re-fed for 24 hours after 24 hours of fasting, and the small intestine was analyzed. GLP-2(3-33) also was injected into rats for analysis of circulating GLP-2(1-33) levels.

RESULTS

GLP-2(3-33) antagonized the actions of GLP-2(1-33) in vitro and ex vivo. Fasting mice exhibited small intestinal atrophy (37% +/- 1% decrease in small intestinal weight, 19% +/- 2% decrease in crypt-villus height, and 99% +/- 35% increase in villus apoptosis, P < .05-.01). Adaptive growth in re-fed mice restored all these parameters, as well as crypt-cell proliferation, to normal control levels (P < .05 vs. fasting); these adaptive changes were prevented partially or completely by co-administration of GLP-2(3-33) to refeeding mice (by 32% +/- 19% to 103% +/- 15%, P < .05-.01 vs re-fed mice). Exogenous GLP-2(3-33) did not affect endogenous GLP-2(1-33) levels.

CONCLUSIONS

These data show that endogenous GLP-2 regulates the intestinotropic response in re-fed mice through modulation of crypt-cell proliferation and villus apoptosis. GLP-2 is therefore a physiologic regulator of the dynamic adaptation of the gut mucosal epithelium in response to luminal nutrients.

Effects of delayed placement on intestinal characteristics in turkey poults

To determine the effects of delayed access to feed on intestinal villus development, bacterial translocation, and salmonella attachment potential in turkey poults, poults were given ad libitum access to water and feed immediately after hatch (FED) or were delayed access to water and feed for 48 h (DLY). In experiment 1, FED poults were heavier until 5 d postfeeding at which time villi were 50 microm longer and 6.8 microm wider, crypts were 5.9 microm deeper, and there were more goblet cells per villus than in the DLY poults. The DLY poults also had reduced numbers of proliferating enterocytes in the villus and higher apoptotic labeling at 1, 2, and 5 d postfeeding. In experiment 2, DLY poults had higher numbers of aerobic bacteria in the ileal digesta and ileal tissue when compared with the FED poults at 1 d postfeeding. To study salmonella attachment potential to the ileum, a segment of the ileum was inoculated with a salmonella culture, incubated for 1 h at 37 degrees C, and flushed; the tissue was homogenized, and numbers of remaining salmonella were enumerated. No differences in salmonella attachment potential were noted between FED and DLY poults. In conclusion, early access to ad libitum feed in poults stimulated growth and development of small intestinal villi and their absorptive surfaces, whereas delayed access to feed resulted in delayed enterocyte proliferation and greater enterocyte apoptosis during the first week posthatch as well as greater numbers of aerobic bacteria associated with the small intestine shortly after hatch.

Role of sirtuin proteins in life extension by caloric restriction

The deacetylase activity of sirtuin proteins may play a key role in the life extending action of caloric restriction in organisms ranging from yeast to mammals. Recent research has been focused on the possible afferent pathway by which caloric restriction increases the deacetylase activity and on the efferent pathway by which the increased deacetylase activity extends life. Further research is needed to firmly establish the role of sirtuin proteins in life extension by caloric restriction in mammals.

Effects of incremental starvation on gut mucosa

Starvation induces gut mucosal atrophy, but the effects of progressive dietary restriction are not defined. The study's purpose was to determine the effects of incremental starvation on gut epithelial cell turnover. After food intake of mice was determined, they were divided into five groups: control (ad libitum fed), 75% normal intake, 50% intake, 25% intake, and fasted. Mice were killed after 48 hours, and the proximal small bowel were assessed for weight and protein content. Histologic specimens were examined for villus morphology, apoptosis, and proliferation. After 48 hr of diet restriction, bowel weight decreased in the 50% intake, 25% intake, and fasted groups. Villus density also decreased in the fasted group. Proliferation progressively decreased in the diet-restricted groups. Apoptosis increased in the fasted group, primarily in the villus tip. In conclusion, incremental starvation produces progressive small bowel atrophy. The mechanism involves both decreased gut epithelial cell proliferation and increased apoptosis.

Inhibition of H2O2-induced apoptosis of lymphocytes by calorie restriction during aging

Calorie restriction (CR) is known to delay the aging process in rodents and is postulated to act by decreasing free radical generation and increasing antioxidant enzyme activity. The present study was designed to investigate the effect of CR and age on oxidative stress-induced apoptosis and associated changes in the levels of TNF-alpha, and Bcl-2 in splenic T lymphocytes. Ad libitum (AL)- or CR-fed C57BL/6J mice were sacrificed either at 6 (young) or 18 (old) months and splenic lymphocytes were incubated with or without 25 micro M H2O2 to induce apoptosis. Apoptosis increased with age in cells of AL-fed mice incubated with H2O2. CR prevented this rise in apoptosis in total splenic lymphocytes and in CD4(+) and CD8(+) T lymphocyte subsets either with or without H2O2. Free radicals increased and mitochondrial membrane potential decreased in aged mice. CR prevented these changes and also prevented the age-associated increase in TNF-alpha and loss of Bcl-2 in total splenic lymphocytes and in CD4(+) and CD8(+) lymphocyte subsets. In summary, lymphocytes in aged AL-fed mice were much more susceptible to oxidative stress-induced apoptosis whereas CR normalized apoptosis by preventing the increase in TNF-alpha and the decrease in Bcl-2 associated with aging.

Frequency of proliferation, apoptosis, and their ratio during rat colon carcinogenesis and their characteristic pattern in the dimethylhydrazine-induced colon adenoma and carcinoma

The imbalance between the cell proliferation and cell loss plays a crucial role in the carcinogenesis and tumor progression. However, the direction of these changes is still the matter of discussion. Thus, the aim of this study was to evaluate the proliferative activity, apoptotic activity, and proliferation/apoptosis ratio (P/A) assessed every 6 weeks in the colonic epithelium during 21 weeks of dimethylhydrazine (DMH) treatment in male Wistar rats. Moreover, it is necessary to answer the question whether these analyzed parameters correlate with the grade of differentiation or dysplasia of the induced tumors. It was found that DMH administration enhanced the proliferation in week 12 and 18 when compared with week 6. The proliferation in the control group did not change during the study. Up to week 12 of the experiment, there were no statistically significant differences between proliferative activity in the control and DMH-treated groups. In week 18, the proliferation in DMH-treated group was higher than in the control group. At all time points of the study, the apoptotic activity in the DMH-treated groups was significantly higher than in controls and in both groups, they dropped during the study. In the control group, apoptotic activity decreased in week 18 and was lower in comparison to that in week 6 and 12. In the group treated with DMH, apoptosis dropped at week 12 and was lower than in week 6. The P/A ratio did not change during the study in the control group, but increased in the DMH-treated group. After 21 weeks of DMH administration, 28 cases of colon adenocarcinoma and nine cases of colon adenoma were obtained and classified according to the WHO classification (1989) for human colon tumors. The adenocarcinomas were divided into four groups: well, moderately, poorly differentiated, and signet-ring cell carcinoma. The colon adenomas were divided into three groups: adenoma with mild, moderate, and severe grade of dysplasia. The proliferative activity in signet-ring cell carcinoma was significantly smaller than in well, moderately, and poorly differentiated adenocarcinoma and apoptotic activity was smaller than in well-differentiated adenocarcinoma. A weak (statistically nonsignificant) negative correlation was also observed between the proliferative and apoptotic activity in adenocarcinoma or adenoma and their grade of dedifferentiation or dysplasia, respectively.

Age-related death-survival balance in myocardium: an immunohistochemical and biochemical study

During ageing, the occurrence of apoptosis is due to a progressive impairment of normal functions, leading to eliminate redundant, damaged or infected cells. Here we report that also in myocardial tissue, ageing, besides reduction of the number of myocytes and of specialized conduction tissue cells, reduction in Ca(++) transport across the membrane, includes the establishment of apoptosis. In particular, the occurrence of this process, which is less represented than we would have expected, is mediated by the balance between the well known Bcl-2 protein family members, Bad, Bax and Bcl-2, related to the pathway PI-3-kinase/AKT-1, which is known to deliver a survival signal. In fact, aged myocardial cells disclose a suboptimal response, which underlines the possibility that they can become more sensitive to damaging factors or diseases, more frequently occurring during ageing, probably due to an exploited molecular control of apoptosis.

Restoration of the jejunal mucosa in rats refed after prolonged fasting

To investigate the importance of body fuel depletion on gut rehabilitation after food deprivation, we compared the kinetics of jejunal mucosa alteration and restoration in rats that were refed after reaching different stages in body fuel depletion. Rats (P2) were refed while still in the so-called phase II, where body protein utilization is minimized, whereas rats (P3) were refed when they had reached the stage of increasing protein utilization (phase III). There was a significant decrease in total mass of intestine (P2, -30%; P3, -40%) and jejunal mucosa (P2, -52%; P3, -60%), as well in the size of the crypts (P2, -15%; P3, -36%) and villi (P2, -37%; P3, -55%). Structural changes of the mucosa included disappearance of some villi and a reduction in the size and number of crypts. Despite the larger morphological alterations in P3, the restoration of mucosa was as fast and complete after only 3 days of refeeding for both P2 and P3 rats. The respective roles of the mitosis pressure and of the lamina propria dynamics were studied. The rapid reversibility of the gut mucosal alterations due to fasting might constitute an integrative process.

Cell proliferation, apoptosis, NF-kappaB expression, enzyme, protein, and weight changes in livers of burned rats

Thermal injury has been shown to alter gut epithelium and heart myocyte homeostasis by inducing programmed cell death. The effect of thermal injury on hepatocyte apoptosis and proliferation, however, has not been established. The purpose of this study was to determine whether a large thermal injury increases liver cell apoptosis and proliferation and whether these changes were associated with alterations in hepatic nuclear factor kappaB (NF-kappaB) expression and changes in liver enzymes and amount of protein. Sprague-Dawley rats received a 40% total body surface area scald burn or sham burn. Rats were killed and livers were harvested at 1, 2, 5, and 7 days after burn. Liver cell apoptosis was determined by terminal deoxyuridine nick end labeling (TUNEL) assay and cell proliferation by immunohistochemistry for proliferating cell nuclear antigen. Hepatic NF-kappaB expression was determined by Western blot, and total hepatic protein content was determined by protein assay. Protein concentration decreased after burn compared with sham controls (P < 0.05). Liver cell apoptosis, proliferation, and NF-kappaB expression in hepatocytes increased in burned rats compared with controls (P < 0.05). It was concluded that thermal injury induces hepatic cell apoptosis and proliferation associated with an increase in hepatic NF-kappaB expression and a decrease in hepatic protein concentration.

Effects of aging on expression of genes involved in regulation of proliferation and apoptosis in the colonic epithelium

The purpose of this study was to characterize the effects of aging on colonic messenger ribonucleic acid (mRNA) and protein levels of genes involved in the regulation of cell proliferation and apoptosis, and epithelial morphology in male Fischer 344 rats. Our study shows that, with aging, colonic expression of insulin-like growth factor-1 (IGF-1) and IGF-binding protein-3 (IGFBP-3) is significantly increased and decreased, respectively. Colonic Bax protein levels are increased significantly with aging. Immunohistochemical localization of Bax protein shows a greatly increased expression in colonic crypts, especially in the upper portion of crypts. p53 expression is unchanged with aging. No significant change in proliferation of colonic crypt cells is observed by bromodeoxyuridine (BrdU) labeling, although the increased colonic expression of IGF-1 and the decreased expression of IGFBP-3 with aging may result in an increased colonic IGF-1 bioactivity. The age-related changes in Bax and IGFBP-3 appear to be independent of p53. The finding of an unchanged colonic epithelium with aging in the face of a greatly increased Bax protein levels may suggest that the elevated Bax protein levels function to render colonic epithelial cells more sensitive to apoptotic stimuli.

Influence of short-term repeated fasting on the longevity of female (NZB x NZW)F1 mice

Caloric restriction in rodents is well known to retard the rate of aging, increase mean and maximum life-spans, and inhibit the occurrence of many age-associated diseases. However, little is known about the influence of short-term repeated fasting on longevity. In this study, female (NZB x NZW)F1 mice were used to test the physiological effect of short-term repeated fasting (4 consecutive days, every 2 weeks). The results showed that fasting mice survived significantly longer than the full-fed mice, in spite of the fasting group having a heavier body weight than the control group. Mean survival times for fasting and control mice were 64.0+/-15.3 and 47.9+/-9.4 weeks, respectively. Short-term repeated fasting manipulation was also effective on the prolongation of life-span in autoimmune-prone mice.

Apoptosis: a two-edged sword in aging

Here we summarize briefly what is known about both the positive and negative impacts of apoptosis during aging in mammalian systems and also update an earlier review. It is important to understand both of these impacts to devise useful interventions. Such interventions include both physiological and molecular approaches, including transgenic interventions. The critical roles of the mitochondria in both generating reactive oxygen species, and in initiating apoptosis are recognized, suggesting that maintaining mitochondrial function could be an important therapeutic goal, especially in post-mitotic tissues. In contrast, the ability to eliminate unwanted, damaged and dysfunctional cells through apoptosis has anti-aging implications in mitotic tissues.