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Effects of diet composition and adrenalectomy on the lipogenic responses of rats to starvation-refeeding.

The interacting effects of diet and glucocorticoid (GC) on the tritium incorporation into lipid and glucose-6-phosphate dehydrogenase activity in starved-refed rats was studied. Male Sprague-Dawley rats were intact, adrenalectomized (ADX), or ADX and given GC and fed either ad libitum or not fed for 48 hours amd refed either a 65% glucose diet, 65% sucrose diet, 65% starch diet, 65% protein diet or a 40% fat diet. No diet differences in rates of 3HOH incorporation into total lipids were observed in ad libitum-fed rats. ADX lowered lipogenesis and this effect was diet dependent. Sucrose-fed, glucose-fed and protein-fed ADX rats had lower rates of lipogenesis than their intact controls. Starvation-refeeding increased lipogenesis in all groups of intact rats except those fed the 40% fat diet. The magnitude of the response was diet dependent. Sucrose-fed rats had greater responses than fat-fed rats. The diet effect was dependent on the presence of the adrenals and GC. Thus, the large increase in liver lipid associated with starvation-refeeding is contingent on the composition of the diet and the presence of the adrenals.

Adrenalectomy↗

Effect of starvation and refeeding on activity of a Ca2+-dependent protease in rat skeletal muscle.

The effects of starving, refeeding, and restarving rats for different periods on content of sarcoplasmic and contractile proteins and on activity of the Ca2+-dependent proteinase (CAF) in skeletal muscle was determined. Groups of five to six male rats, 8 to 11 weeks old, were starved up to 8 days, refed up to 6 days, and in two experiments, restarved up to 10 days. CAF activity was assayed in P 0-45 crude CAF fractions prepared so as to remove a protein inhibitor of CAF; the assays were demonstrated to be specific for CAF. Sarcoplasmic protein content of rat skeletal muscle changed little until after 6 days of restarvation when it decreased to 68-89% of control level (P less than 0.05). Contractile protein content decreased to 65% of control level (P less than 0.01) after 8 days of starvation, remained at this level for 4 days of refeeding, then increased to approximately 80% of control level after 6 days of refeeding, remained at this level for 2 days of restarvation, and then decreased to approximately 65% of control level (P less than 0.01) after 6 and 8 days of restarvation. Muscle CAF activity did not change during the first 8 days of starvation but increased to 113% above control level (P less than 0.01) after 6 days refeeding and then decreased to only 29% of control level (P less than 0.01) after 8 days of restarvation. These changes in muscle CAF activity are consistent with the proposed role for CAF in initiating metabolic turnover of contractile proteins, but because actual measurements of myofibrillar protein were not made and because in vivo CAF activity is difficult to assess, they do not prove this role for CAF nor do they exclude participation of other proteinases.

Animals↗

Effect of starvation on the disposition of free and peptide-linked trimethyllysine in the rat.

Free and peptide-linked trimethyllysine were measured in fed and 5-d starved rats. The trimethyllysine content of liver and kidney was significantly increased on d 5 of starvation to two to three times the levels found in fed animals. Skeletal muscle of fed rats contained over six times as much trimethyllysine (19.3 nmol/g) as that found in liver (3.2 nmol/g) or kidney (2.7 nmol/g). Plasma free trimethyllysine significantly increased from 1 nmol/ml in fed rats to 2.2 nmol/ml in 5-d starved rats. During this same period, daily total trimethyllysine excretions averaged approximately 400 nmol/d. Urinary free trimethyllysine was significantly depressed during starvation. Assuming that trimethyllysine in plasma does not exist in a protein-bound form, clearance calculations based on concentrations of plasma and urinary trimethyllysine indicated that this compound is readily reabsorbed by the kidney. As previous studies have indicated that trimethyllysine is not readily absorbed by other tissues, this indicates that the kidney may be the primary regulatory site for the disposition free of free trimethyllysine in plasma and urine. Estimates of the efficiency of entry of trimethyllysine into the carnitine biosynthetic pathway were calculated and ranged from 41% in 3-d starved rats to 80% in fed rats. We conclude that carnitine biosynthesis is limited by the availability of trimethyllysine, which, in the starved rat, is limited by the rate of protein turnover.

Animals↗

Effects of food restriction and starvation-refeeding on volatile fatty acid concentrations in the rat.

Adult male rats were fed either ad libitum or at levels of 19 or 15 g of nonpurified diet per rat daily or subjected to 48 h of starvation followed by 24 h of refeeding. Concentrations of total and individual volatile fatty acids (VFA) in cecal contents were higher in rats fed ad libitum than in those restricted to 19 or 15 g/d. Only butyrate concentration was lower in rats given 15 g/d than in those given 19 g/d. In starved animals all cecal VFA declined within 24 h of food removal, but the greatest change was in butyrate, which fell to less than 12% of the initial value. Acetate and propionate fell further after 48 h, but their concentrations were restored to control values within 24 h of refeeding while butyrate remained depressed by 50%. Cecal pH was closely related to total VFA concentration, although the highest degree of correlation was with butyrate. Hepatic portal venous plasma VFA concentrations generally reflected those in cecal digesta except that the proportion of butyrate was relatively lower in this blood vessel than in cecal contents. Under all conditions acetate was the only VFA found in arterial plasma and in the fully fed state was lower than in hepatic portal venous plasma. Food restriction and starvation did not alter arterial concentrations, indicating abolition of net uptake. We conclude that all VFA are affected by availability of fermentable material to the large bowel microflora but that the disproportionate changes in butyrate may reflect preferential use of this acid by cells of the large bowel wall.

Animals↗

Differential effects of adrenalectomy and starvation-refeeding on hepatic lipogenic responses to dehydroepiandrosterone and glucocorticoid in BHE and Sprague-Dawley rats.

The interaction of rat strain and glucocorticoid status on the dehydroepiandrosterone (DHEA)-mediated decrease in response to starvation-refeeding was studied. DHEA treatment of intact starved-refed Sprague-Dawley rats resulted in significantly lower hepatic lipid and glucose-6-phosphate dehydrogenase activity than observed in non-DHEA-treated rats. When Sprague-Dawley rats were adrenalectomized (ADX), the response to DHEA treatment was potentiated. If glucocorticoid was replaced, there was some amelioration of the DHEA effect in the ADX rats. Responses to DHEA in BHE rats subjected to the above paradigms were different. The responses of starved-refed BHE rats to DHEA were more pronounced and it appeared that glucocorticoid replacement was not as effective in overcoming DHEA in these rats. Thus, it appears that the comparative inhibition of the glucocorticoid-mediated response to starvation-refeeding by DHEA is strain dependent.

Adrenalectomy↗

Differential regulation of the degradation of myofibrillar and total proteins in skeletal muscle of rats: effects of streptozotocin-induced diabetes, dietary protein and starvation.

In order to examine the effects of streptozotocin-induced diabetes, dietary protein, and starvation on protein degradation in skeletal muscle of perfused rat hindquarters, rates of myofibrillar and total protein degradation were estimated from the release of 3-methylhistidine (N tau-methylhistidine, 3-MH) and tyrosine, respectively. In rats fed a 20% protein diet (controls), the fractional degradation rate of myofibrillar protein was approximately 56% of the total muscle protein. In streptozotocin-induced diabetic rats, 3-MH release by perfused muscle increased significantly on d 1 of treatment and sustained a high level thereafter. By contrast, tyrosine release did not change. Feeding a 50% protein diet for 1 wk altered neither 3-MH nor tyrosine release. Protein-free feeding, though, suppressed tyrosine release to 49% of controls, but did not affect 3-MH release. Starvation for 3 d did not affect tyrosine release, but did increase 3-MH release to 203% of controls. These results indicate that in diabetic and starved rats myofibrillar protein is preferentially degraded, while in protein-deficient rats, non-myofibrillar protein degradation is selectively suppressed. From these observations, we conclude that the degradation of myofibrillar and non-myofibrillar proteins in skeletal muscle can be differentially regulated.

Animals↗

Acid-induced gastric damage in rats is aggravated by starvation and prevented by several nutrients.

The aggravation of acid-induced gastric damage and its prevention by glucose, ascorbate or glutathione precursors was studied in fed and food-deprived rats. The stomachs of fed rats and those starved for 1, 3 or 5 d were vagotomized just before irrigating for 3 h with solutions containing 0-150 mmol HCI/L. Mucosal glutathione, mucus, lipid peroxides and acid back-diffusion were measured. Stomach ulcers were evaluated by morphological and histological examination. The preventive effects of glucose, ascorbate and a mixture of L-glutamine, L-glycine and L-cysteine were evaluated in the stomachs of rats that were starved for 5 d, vagotomized, then perfused for 3 h with 100 mmol HCI/L. Greater acid back-diffusion and ulcer formation, and lower glutathione and mucus levels in starved rats were dependent on the duration of starvation and luminal acidity. Increased acid back-diffusion and decreased glutathione and mucus production were negatively correlated (r < -0.80, P < 0.05) with ulcer formation. A significant enhancement in mucosal lipid peroxide concentration and serious damage of forestomach and corpus mucosal cells were observed in starved rats exposed to 100 mmol HCI/L. These ulcerogenic factors were effectively inhibited in acid-perfused stomachs of food-deprived rats by daily intraperitoneal injection of the amino acid mixture (150 mg/kg) or by an average daily consumption via drinking water of glucose (10 g) or ascorbate (1.2 g). Starvation aggravated acid-induced gastric damage and was associated with greater acid back-diffusion and oxygen radical generation, and lower mucosal glutathione and mucus production.

Amino Acids↗

Metallothionein in mice reduces intestinal zinc loss during acute endotoxin inflammation, but not during starvation or dietary zinc restriction.

Normal metallothionein [(MT)+/+] and MT-null (MT-/-) mice were used to examine the influence of MT on Zn retention and the metabolic consequences of 2 d food deprivation, with and without inflammation induced by intraperitoneal injection of bacterial endotoxin lipopolysaccharide (LPS). LPS reduced fecal Zn concentration in MT+/+ mice from 5.9 +/- 0.2 micromol/g on d 1 to 2.2 +/- 0.2 micromol/g on d 2, but not in MT-/- mice, 5.9 +/- 0.2 and 5.7 +/- 0. 5 micromol/g, respectively. MT+/+ mice fed an 8 mg Zn/kg diet and injected with LPS excreted 40% less Zn over 2 d than their MT-/- counterparts. Starvation for 2 d did not lower fecal Zn concentration in either genotype, although in MT+/+ mice, urinary Zn excretion was reduced from 12.7 +/- 1.3 nmol on d 1 to 5.9 +/- 1.8 nmol on d 2 and plasma Zn concentration was lowered to 9.8 +/- 0.4 micromol/L. Zn was not reduced in urine or plasma of MT-/- mice, with respective values of 10.8 +/- 2.0 nmol on d 1, 9.3 +/- 2.9 nmol on d 2 and 13.0 +/- 1.0 micromol/L. LPS injection resulted in much higher total liver Zn (677 +/- 27 nmol) and MT (106 +/- 2 nmol Cd bound/g) than starvation (Zn = 405 +/- 21, MT = 9 +/- 3) in MT+/+ mice after 2 d, but did not further reduce urinary Zn. LPS-injected MT-/- mice had no rise in liver Zn or fall in plasma and urine Zn. MT-/- mice fed a Zn-deficient (0.8 mg Zn/kg) diet lost 10% of body weight over 25 d compared with no loss in MT+/+ mice. Despite this, MT-/- mice excreted no more Zn via the gut than did MT+/+ mice. In summary, MT inhibits intestinal Zn loss when highly expressed. When uninduced, typically during Zn deficiency, MT appears to conserve Zn and body mass by reducing only urinary and other nonintestinal Zn losses.

Animals↗

Starvation and feeding a high-carbohydrate, low-fat diet regulate the expression sterol regulatory element-binding protein-1 in chickens.

In mammalian liver, the mature form of sterol regulatory element-binding protein-1c (SREBP-1c) is an important activator of a wide array of genes involved in triacylglycerol biosynthesis. Starvation and feeding a high-carbohydrate, low-fat diet modulate the concentration of mature SREBP-1c primarily by a pretranslational mechanism. It is not known whether alterations in nutritional status regulate the concentration of SREBPs in nonmammalian species. In this study, we found that in previously starved chicks, feeding a high-carbohydrate, low-fat diet stimulated a robust increase (14-fold at 5 h of feeding) in the concentration of mature SREBP-1 in liver. Feeding a high-carbohydrate, low-fat diet also increased the concentration of precursor SREBP-1 and SREBP-1 messenger RNA in chick liver; however, the magnitude of this effect was substantially lower than that observed for mature SREBP-1. DNA binding experiments demonstrated that 3 protein complexes containing SREBP bound the acetyl-CoA carboxylase-alpha (ACCalpha) sterol regulatory element (SRE) in chick liver and that the binding activity of 2 of these complexes was increased by consumption of a high-carbohydrate, low-fat diet. Additional analyses showed that feeding a high-carbohydrate, low-fat diet had no effect on the concentration of mature SREBP-2 and the binding of SREBP-2 to the ACCalpha SRE in chick liver. These results indicate that alterations in the concentration of mature SREBP-1 play a role in mediating the effects of starvation and feeding a high-carbohydrate, low-fat diet on ACCalpha transcription in chick liver and that diet-induced changes in mature SREBP-1 concentration in chick liver are mediated primarily by a posttranslational mechanism.

Acetyl-CoA Carboxylase↗

Effect of ammonia starvation on hydroxylamine oxidoreductase activity of Nitrosomonas europaea.

A technique for detection of the activity of hydroxylamine oxidoreductase (HAO) involving denaturing SDS-polyacrylamide gels was developed. The activity of HAO of Nitrosomonas europaea was assayed using this technique, which revealed a single active band of 140 kDa. The HAO activity of other ammonia-oxidizers was also resistant to SDS, the molecular weights being identical to that of N. europaea. N. europaea cells starved of ammonia for up to 72 h retained a considerable amount of HAO, as detected on Western blot analysis, and a significant level of its activity, as found on assaying at the end of the starvation period. Only after 4 h incubation of starved N. europaea cells with 2.0 mM ammonia was some increase in the HAO level observed. The results indicate that HAO remains highly stable during ammonia starvation of N. europaea.

Ammonia↗

Effect of starvation and refeeding on autophagy and heterophagy in rat liver.

Increase in the density of liver lysosomes after leupeptin administration was marked in starved rats but only slight in starved-refed rats. The levels of several intracellular enzymes in the liver lysosome fraction purified from leupeptin-treated rats were about 10 to 30 times more in starved rats than in refed rats. However, there was no difference between the intralysosomal levels of endocytosed FITC-labeled asialofetuin in starved and refed rats, indicating that refeeding after starvation markedly suppressed autophagy but not heterophagy in vivo. Immunohistochemical studies with cathepsin B and asialofetuin Fab'-peroxidase conjugates showed that refeeding after starvation markedly altered the cellular distribution of cathepsin B in the liver, resulting in a linear arrangement of the enzyme only on the periphery of hepatocytes. In contrast, endocytosed asialofetuin was found only in the periphery of hepatocytes of both starved and starved-refed rats. These results indicate that autophagy and heterophagy are regulated by different mechanisms in vivo.

Animals↗

Influence of starvation, surgery, and sepsis on cardiac protein synthesis in rats: effects of parenteral nutrition, glutamine, and growth hormone.

The effect of sepsis on the rate of protein synthesis in the heart is poorly described. We have investigated changes in protein synthesis in the ventricles of the heart over time after cecal ligation and puncture (CLP) in rats in comparison with sham-operated and unoperated animals (ad libitum). All operated animals were starved from the time of surgery to the time of sacrifice. When operated animals were compared with ad libitum animals, ventricular weight and ventricular protein, and DNA and RNA contents were unchanged at 24 h, but were invariably reduced at 72 and 96 h. Fractional rate of protein synthesis (FSR), RNA activity, and cellular efficiency were reduced at 24 h and further reduced at 72 and 96 h. There were no differences, however, between septic and sham-operated animals. Eighteen hours after CLP, additional groups of rats were infused intravenously with 0.9% sodium chloride, parenteral nutrition (PN), or PN with glutamine, and were given a single dose of 400 microg recombinant human growth hormone (rhGH) or an equal volume of 0.9% sodium chloride. FSR was higher in animals given PN when compared with those given 0.9% sodium chloride only, and did not differ from FSR measured in unoperated animals. There was no additional benefit from the acute administration of either glutamine-enriched PN or rhGH. These results indicate that ventricular protein synthesis is markedly reduced by surgery and starvation, but that superimposed sepsis does not further influence these changes. PN can prevent the fall in cardiac protein synthesis associated with starvation, surgery, and sepsis, but neither glutamine nor rhGH produced any additional benefit.

Animals↗

Managing uncertainty: information and insurance under the risk of starvation.

In an uncertain world, animals face both unexpected opportunities and danger. Such outcomes can select for two potential strategies: collecting information to reduce uncertainty, or insuring against it. We investigate the relative value of information and insurance (energy reserves) under starvation risk by offering model foragers a choice between constant and varying food sources over finite foraging bouts. We show that sampling the variable option (choosing it when it is not expected to be good) should decline both with lower reserves and late in foraging bouts; in order to be able to reap the reduction in uncertainty associated with exploiting a variable resource effectively, foragers must be able to afford and compensate for an initial increase in the risk of an energetic shortfall associated with choosing the option when it is bad. Consequently, expected exploitation of the varying option increases as it becomes less variable, and when the overall risk of energetic shortfall is reduced. In addition, little activity on the variable alternative is expected until reserves are built up early in a foraging bout. This indicates that gathering information is a luxury while insurance is a necessity, at least when foraging on stochastic and variable food under the risk of starvation.

Animals↗

Immune response to parasitism reduces resistance of Drosophila melanogaster to desiccation and starvation.

In natural populations, organisms experience simultaneously biotic (e.g., competitors and parasites) and abiotic (e.g., temperature and humidity) stresses. Thus, species must have the capacity to respond to combinations of stressors. How does interaction between biotic and abiotic stress affect organismal performance? To address this question, I studied stress resistance of adult Drosophila melanogaster that survived parasitic attack (as larvae) by the parasitoid Asobara tabida. To determine the impact of genotype on stress resistance. I measured survival under desiccation and starvation of flies within isofemale (genetic) lines. Survivors of parasitism had slightly reduced survivorship compared to unparasitized relatives when both were unstressed, and this difference was exacerbated by desiccation and starvation. These results indicate multiple stressors can compound each other's individual negative effects on fitness. Moreover, isofemale lines differed in their sensitivity to environmental stress and to parasitism. Consequently, genotypic differences in sensitivity to stress may reflect differences in investment priorities between traits that promote survival over other life-history characters.

Animals↗

Effects of starvation on cardiovascular function (including the mammary circulation) and water balance in pregnant goats.

In conscious goats, starved for 48 hr, in mid-pregnancy (70 days) cardiac output and blood volume decreased; total peripheral resistance increased; heart rate, stroke volume, blood pressure, mammary blood flow and mammary resistance were not significantly affected. In late pregnancy (132 days) cardiac output, heart rate, blood volume and mammary blood flow fell; peripheral resistance increased; stroke volume and blood pressure were not significantly affected. In mid-pregnancy, water consumption fell and the animal entered a stage of negative sensible water balance which persisted for both days of starvation. A similar change was obtained on the first day in late-pregnant goats, but on the second day water consumption increased and positive water balance was restored. Cardiac output, heart rate, blood volume and mammary blood flow was higher in fed late-pregnant than in fed mid-pregnant goats, total peripheral resistance was lower while there were no significant changes in stroke volume or blood pressure. Indications of correlations between litter size and cardiac function were obtained. The results are compared with previous studies on the effects of starvation in lactating animals and are discussed in relation to the control of cardiac function and mammary blood flow in pregnancy and lactation.

Animals↗

Differential effects of temperature and starvation on induction of the viable-but-nonculturable state in the coral pathogens Vibrio shiloi and Vibrio tasmaniensis.

We compared induction of the viable-but-nonculturable (VBNC) state in two Vibrio spp. isolated from diseased corals by starving the cells and maintaining them in artificial seawater at 4 and 20 degrees C. In Vibrio tasmaniensis, isolated from a gorgonian octocoral growing in cool temperate water (7 to 17 degrees C), the VBNC state was not induced by incubation at 4 degrees C after 157 days. By contrast, Vibrio shiloi, isolated from a coral in warmer water (16 to 30 degrees C), was induced into the VBNC state by incubation at 4 degrees C after 126 days. This result is consistent with reports of low-temperature induction in several Vibrio spp. A large proportion of the V. tasmaniensis population became VBNC after incubation for 157 days at 20 degrees C, and V. shiloi became VBNC after incubation for 126 days at 20 degrees C. Resuscitation of V. shiloi cells from cultures at both temperatures was achieved by nutrient addition, suggesting that starvation plays a major role in inducing the VBNC state. Our results suggest that viable V. shiloi could successfully persist in the VBNC state in seawater for significant periods at the lower temperatures that may be experienced in winter conditions, which may have an effect on the seasonal incidence of coral bleaching. For both species, electron microscopy revealed that prolonged starvation resulted in transformation of the cells from rods to cocci, together with profuse blebbing, production of a polymer-like substance, and increased membrane roughness. V. shiloi cells developed an increased periplasmic space and membrane curling; these features were absent in V. tasmaniensis.

Animals↗

Galactose starvation in a bloodstream form Trypanosoma brucei UDP-glucose 4'-epimerase conditional null mutant.

Galactose metabolism is essential for the survival of Trypanosoma brucei, the etiological agent of African sleeping sickness. T. brucei hexose transporters are unable to transport galactose, which is instead obtained through the epimerization of UDP-glucose to UDP-galactose catalyzed by UDP-glucose 4'-epimerase (galE). Here, we have characterized the phenotype of a bloodstream form T. brucei galE conditional null mutant under nonpermissive conditions that induced galactose starvation. Cellular levels of UDP-galactose dropped rapidly upon induction of galactose starvation, reaching undetectable levels after 72 h. Analysis of extracted glycoproteins by ricin and tomato lectin blotting showed that terminal beta-d-galactose was virtually eliminated and poly-N-acetyllactosamine structures were substantially reduced. Mass spectrometric analysis of variant surface glycoprotein confirmed complete loss of galactose from the glycosylphosphatidylinositol anchor. After 96 h, cell division ceased, and electron microscopy revealed that the cells had adopted a morphologically distinct stumpy-like form, concurrent with the appearance of aberrant vesicles close to the flagellar pocket. These data demonstrate that the UDP-glucose 4'-epimerase is essential for the production of UDP-galactose required for galactosylation of glycoproteins and that galactosylation of one or more glycoproteins, most likely in the lysosomal/endosomal system, is essential for the survival of bloodstream form T. brucei.

Animals↗

Identification of sulfate starvation-regulated genes in Escherichia coli: a gene cluster involved in the utilization of taurine as a sulfur source.

Genes whose expression is regulated by sulfate starvation in Escherichia coli were identified by generating random translational lacZ fusions in the chromosome with the lambda placMu9 system. Nine lacZ fusion strains which expressed beta-galactosidase after growth under sulfate starvation conditions but not after growth in the presence of sulfate were found. These included two strains with insertions in the dmsA and rhsD genes, respectively, and seven strains in which the insertions were located within a 1.8-kb region downstream of hemB at 8.5 minutes on the E. coli chromosome. Analysis of the nucleotide sequence of this region indicated the presence of four open reading frames designated tauABCD. Disruption of these genes resulted in the loss of the ability to utilize taurine (2-aminoethanesulfonate) as a source of sulfur but did not affect the utilization of a range of other aliphatic sulfonates as sulfur sources. The TauA protein contained a putative signal peptide for transport into the periplasm; the TauB and TauC proteins showed sequence similarity to ATP-binding proteins and membrane proteins, respectively, of ABC-type transport systems; and the TauD protein was related in sequence to a dichlorophenoxyacetic acid dioxygenase. We therefore suggest that the proteins encoded by tauABC constitute an uptake system for taurine and that the product of tauD is involved in the oxygenolytic release of sulfite from taurine. The transcription initiation site was detected 26 to 27 bp upstream of the translational start site of tauA. Expression of the tauD gene was dependent on CysB, the transcriptional activator of the cysteine regulon.

Amino Acid Sequence↗