Resistance and augmentation of innate immunity in mice exposed to starvation

Dietary protein enhances non-specific immunity, anti-oxidative capability and resistance to Aeromonas hydrophila in Labeo rohita fingerlings pre-exposed to short feed deprivation stress

Present experiment was conducted to study the effect of dietary protein levels on growth, immunity and anti-oxidative status of Labeo rohita fingerlings during feed deprivation followed by refeeding. Fish (5.44 ± 0.10 g) were deprived of feed for 3 weeks and then re-fed to satiation for 5 weeks with one of the diets containing 25 (25P), 30 (30P), 35 (35P) or 40 (40P) percent crude protein (CP) level. In addition to these groups, a control group (C) was also maintained by feeding to satiation level twice daily with a diet containing 30% CP throughout the experimental period. At the end of 8-weeks' trial, fish were challenged with Aeromonas hydrophila and survival was recorded for the next 7 days. Complete recovery of growth in terms of weight gain percentage was achieved in the fish fed 35 and 40% protein during refeeding. The body indices (condition factor and hepatosomatic index), haematological parameters and serum protein contents at the end of the experimental trial were not significantly different (P > 0.05) among different groups suggesting that the overall health of the fish was not compromised. However, respiratory burst activity and serum lysozyme activity were indicative of a better immune function in the higher protein fed groups (35P and 40P) than the lower protein groups (25P and 30P). Following challenge with Aeromonas hydrophila, survival rate, blood monocyte%, respiratory burst activity, serum lysozyme activity, serum protein and globulin were significantly higher (P < 0.05) in the 35P and 40P groups compared to the other groups. Further, fish fed lower dietary protein were not able to restore the activities of anti-oxidative enzymes (superoxide dismutase and catalase) in the liver. Conclusively, an improved disease resistance capability and immune status was observed in the fish fed a higher dietary protein (35-40%), even out-performing the daily-fed fish.

Fasting enhances TRAIL-mediated liver natural killer cell activity via HSP70 upregulation

Acute starvation, which is frequently observed in clinical practice, sometimes augments the cytolytic activity of natural killer cells against neoplastic cells. In this study, we investigated the molecular mechanisms underlying the enhancement of natural killer cell function by fasting in mice. The total number of liver resident natural killer cells in a unit weight of liver tissue obtained from C57BL/6J mice did not change after a 3-day fast, while the proportions of tumor necrosis factor-related apoptosis-inducing ligand (TRAIL)+ and CD69+ natural killer cells were significantly elevated (n = 7, p <0.01), as determined by flow cytometric analysis. Furthermore, we found that TRAIL- natural killer cells that were adoptively transferred into Rag-2-/- γ chain-/- mice could convert into TRAIL+ natural killer cells in fasted mice at a higher proportion than in fed mice. Liver natural killer cells also showed high TRAIL-mediated antitumor function in response to 3-day fasting. Since these fasted mice highly expressed heat shock protein 70 (n = 7, p <0.05) in liver tissues, as determined by western blot, the role of this protein in natural killer cell activation was investigated. Treatment of liver lymphocytes with 50 µg/mL of recombinant heat shock protein 70 led to the upregulation of both TRAIL and CD69 in liver natural killer cells (n = 6, p <0.05). In addition, HSP70 neutralization by intraperitoneally injecting an anti- heat shock protein 70 monoclonal antibody into mice prior to fasting led to the downregulation of TRAIL expression (n = 6, p <0.05). These findings indicate that acute fasting enhances TRAIL-mediated liver natural killer cell activity against neoplastic cells through upregulation of heat shock protein 70.

Fasting protects liver from ischemic injury through Sirt1-mediated downregulation of circulating HMGB1 in mice

BACKGROUND & AIMS

Fasting and calorie restriction are associated with a prolonged life span and an increased resistance to stress. The protective effects of fasting have been exploited for the mitigation of ischemic organ injury, yet the underlying mechanisms remain incompletely understood. Here, we investigated whether fasting protects liver against ischemia reperfusion (IR) through energy-preserving or anti-inflammatory mechanisms.

METHODS

Fasted C57BL6 mice were subjected to partial hepatic IR. Injury was assessed by liver enzymes and histology. Raw264-7 macrophage-like cells were investigated in vitro. Sirt1 and HMGB1 were inhibited using Ex527 and neutralizing antibodies, respectively.

RESULTS

Fasting for one, but not two or three days, protected from hepatic IR injury. None of the investigated energy parameters correlated with the protective effects. Instead, inflammatory responses were dampened in one-day-fasted mice and in starved macrophages. Fasting alone led to a reduction in circulating HMGB1 associated with cytoplasmic HMGB1 translocation, aggregate formation, and autophagy. Inhibition of autophagy re-elevated circulating HMGB1 and abolished protection in fasted mice, as did supplementation with HMGB1. In vitro, Sirt1 inhibition prevented HMGB1 translocation, leading to elevated HMGB1 in the supernatant. In vivo, Sirt1 inhibition abrogated the fasting-induced protection, but had no effect in the presence of neutralizing HMGB1 antibody.

CONCLUSIONS

Fasting for one day protects from hepatic IR injury via Sirt1-dependent downregulation of circulating HMGB1. The reduction in serum HMGB1 appears to be mediated by its engagement in the autophagic response. These findings integrate Sirt1, HMGB1, and autophagy into a common framework that underlies the anti-inflammatory properties of short-term fasting.

Man SN, W. Morni WZ, N.A. Suhaili AS, Cheng SY, Hsu CH. Modulation of innate immunity and gene expressions in white shrimp Litopenaeus vannamei following long-term starvation and re-feeding

The survival rate, weight loss, immune parameters, resistance against Vibrio alginolyticus and white-spot syndrome virus (WSSV), and expressions of lipopolysaccharide- and ß-glucan-binding protein (LGBP), peroxinectin (PX), prophenoloxidase-activating enzyme (ppA), prophenoloxidase (proPO) I, proPO II, α2-macroglobulin (α2-M), integrin ß, heat shock protein 70 (HSP70), cytosolic manganese superoxide dismutase (cytMnSOD), mitochondrial manganese superoxide dismutase (mtMnSOD), and extracellular copper and zinc superoxide dismutase (ecCuZnSOD) were examined in the white shrimp Litopenaeus vannamei (8.18 ± 0.86 g body weight) which had been denied food (starved) for up to 14-28 days. Among shrimp which had been starved for 7, 14, 21, and 28 days, 100%, 90%, 71%, and 59% survived, and they lost 3.2%, 7.3%, 9.2%, and 10.4% of their body weight, respectively. Hyaline cells (HCs), granular cells (GCs, including semi-granular cells), the total haemocyte count (THC), phenoloxidase (PO) activity, respiratory bursts (RBs), and SOD activity significantly decreased in shrimp which had been starved for 1, 1, 1, 5, 14, and 3 days, respectively. The expression of integrin ß significantly decreased after 0.5-5 days of starvation, whereas the expressions of LGBP, PX, proPO I, proPO II, ppA, and α2-M increased after 0.5-1 days. Transcripts of all genes except ecCuZnSOD decreased to the lowest level after 5 days, and tended to background values after 7 and 14 days. Cumulative mortality rates of 7-day-starved shrimp challenged with V. alginolyticus and WSSV were significantly higher than those of challenged control-shrimp for 1-7 and 1-4 days, respectively. In another experiment, immune parameters of shrimp which had been starved for 7 and 14 days and then received normal feeding (at 5% of their body weight daily) were examined after 3, 6, and 12 h, and 1, 3, and 5 days. All immune parameters of 7-day-starved shrimp were able to return to their baseline values after 5 days of re-feeding except for GCs, whereas all parameters of 14-day-starved shrimp failed to return to the baseline values even with 5 days of re-feeding. It was concluded that shrimp starved for 14 days exhibited three stages of modulation of gene expression, together with reductions in immune parameters, and decreased resistance against pathogens.

Effects of short term fasting on the evolution of fecal peritonitis in mice

PURPOSE

To investigate the effect of 72 hours food suppression on the evolution of fecal peritonitis in mice evaluating the mortality and measuring the number and size of abscesses formed into the peritoneal cavity.

METHODS

Mice receiving commercial diet and water ad libitum (control group, N=35) and mice fasted during 72 h (N=35), receiving only water ad libitum, were inoculated by i.p. route, with 4uL/g body weight of a fecal suspension diluted 1:6 or 1:9 in 0.15M NaCl solution (1:6 dilution, 22 controls and 18 fasted; 1:9 dilution, 13 controls and 17 fasted). Animals were followed up until two weeks after fecal inoculation, when the survivors were euthanized for evaluation of the number and size of intra-peritoneal abscesses. Mortality was evaluated by Kaplan Meyer curves.

RESULTS

Mortality was significantly higher in fasted groups than in controls. However the number and size of abscesses were significantly less in fasted groups than in controls.

CONCLUSION

Seventy two hours food suppression increased the susceptibility to endotoxic shock (high mortality after peritonitis induction) and the resistance to infection with fecal microorganisms (less number and size of intra-peritoneal abscesses).

A glycine betaine importer limits Salmonella stress resistance and tissue colonization by reducing trehalose production

Mechanisms by which Salmonella establish chronic infections are not well understood. Microbes respond to stress by importing or producing compatible solutes, small molecules that stabilize proteins and lipids. The Salmonella locus opuABCD (also called OpuC) encodes a predicted importer of the compatible solute glycine betaine. Under stress conditions, if glycine betaine cannot be imported, Salmonella enterica produce the disaccharide trehalose, a highly effective compatible solute. We demonstrate that strains lacking opuABCD accumulate more trehalose under stress conditions than wild-type strains. ΔopuABCD mutant strains are more resistant to high-salt, low-pH and -hydrogen peroxide, conditions that mimic aspects of innate immunity, in a trehalose-dependent manner. In addition, ΔopuABCD mutant strains require the trehalose production genes to out-compete wild-type strains in mice and macrophages. These data suggest that in the absence of opuABCD, trehalose accumulation increases bacterial resistance to stress in broth and mice. Thus, opuABCD reduces bacterial colonization via a mechanism that limits trehalose production. Mechanisms by which microbes limit disease may reveal novel pathways as therapeutic targets.

Fasting vs dietary restriction in cellular protection and cancer treatment: from model organisms to patients

The dietary recommendation for cancer patients receiving chemotherapy, as described by the American Cancer Society, is to increase calorie and protein intake. Yet, in simple organisms, mice, and humans, fasting--no calorie intake--induces a wide range of changes associated with cellular protection, which would be difficult to achieve even with a cocktail of potent drugs. In mammals, the protective effect of fasting is mediated, in part, by an over 50% reduction in glucose and insulin-like growth factor 1 (IGF-I) levels. Because proto-oncogenes function as key negative regulators of the protective changes induced by fasting, cells expressing oncogenes, and therefore the great majority of cancer cells, should not respond to the protective signals generated by fasting, promoting the differential protection (differential stress resistance) of normal and cancer cells. Preliminary reports indicate that fasting for up to 5 days followed by a normal diet, may also protect patients against chemotherapy without causing chronic weight loss. By contrast, the long-term 20 to 40% restriction in calorie intake (dietary restriction, DR), whose effects on cancer progression have been studied extensively for decades, requires weeks-months to be effective, causes much more modest changes in glucose and/or IGF-I levels, and promotes chronic weight loss in both rodents and humans. In this study, we review the basic as well as clinical studies on fasting, cellular protection and chemotherapy resistance, and compare them to those on DR and cancer treatment. Although additional pre-clinical and clinical studies are necessary, fasting has the potential to be translated into effective clinical interventions for the protection of patients and the improvement of therapeutic index.