Mobilization and recovery of energy stores in traíra, Hoplias malabaricus Bloch (Teleostei, Erythrinidae) during long-term starvation and after re-feeding

In some neotropical environments, fishes often experience periods of poor food supply, especially due to extreme fluctuations in rainfall regime. The fish species that experience periods of drought such as the traíra Hoplias malabaricus (Bloch 1794), may stand up to long-term food deprivation. In this study, experiments were performed in order to determine the dynamic of utilization of endogenous reserves in this species during starvation. Adult traíra were both fasted for 30–240 days and re-fed for 30 days following 90 and 240 days of fasting. Glycogen and perivisceral fat were primary energy substrates consumed. During the first 30 days, fish consumed hepatic and muscular glycogen, without exhausting these reserves, and used lipids from perivisceral fat. Hepatic lipids were an important energy source during the first 60 days of starvation and perivisceral fat were consumed gradually, being exhausted after 180 days. Protein mobilization was noticeable after 60 days of fasting, and became the major energy source as the lipid reserves were decreased (between 90 and 180 days). Following the longest periods of food deprivation, fish had utilized hepatic glycogen again. Fish re-fed for 30 days after 90 and 240 days of fasting were able to recover hepatic glycogen stores, but not the other energy reserves.     

条斑紫菜多糖抗疲劳生物活性研究

主要应用活体动物实验技术,研究了纯化产物紫菜多糖的抗疲劳作用及量效关系。通过紫菜多糖PY-G1不同剂量对小鼠游泳时间、乳酸脱氢酶活性、肌糖原和肝糖原含量等指标的检测,分析了紫菜多糖提高小鼠抗疲劳生物活性功能及其量效关系。实验结果表明,紫菜多糖可显著延长小鼠游泳时间,最高可以提高37%;并且可以使小鼠在游泳前后乳酸脱氢酶含量分别增加35%和37.5%(P<0.05);增加小鼠肌糖原储备量和肝糖原储备量,其肌糖原储备量和肝糖原储备量最高可以分别增加85.6%和86%。实验结果表明,条斑紫菜多糖具有明显提高小鼠抗疲劳生物学活性。     

Energetic costs of mate guarding behavior in male stream-dwelling isopods

In the stream-dwelling isopod Lirceus fontinalis, males and females engage in a precopulatory mate guarding phase prior to mating. We examined the energetic costs of mate guarding behavior in males by separately assaying glycogen and lipid content at different time increments following mating. We found that males that had recently mated possessed reduced glycogen reserves and that these reserves were fully replenished within 36 h. Conversely, we found that male lipid reserves were unaffected by time since mating. We concluded that precopulatory mate guarding behavior is energetically costly to males and that glycogen is the energy source utilized to pay that cost. We also examined whether food deprivation during the mate guarding phase affected male energy reserves (glycogen) at the end of that phase. We found that males that were held in the laboratory and starved during mate guarding possessed reduced glycogen at the termination of the phase when compared to fed males. This reduced quantity was equivalent to the glycogen reserves of recently mated males collected from the field. We propose that food deprivation during the mate guarding phase explains the reduction in glycogen reserves at the termination of that phase. We discuss these results with reference to patterns of refuge use behavior during the mate guarding phase.     

Involvement of skeletal muscle protein, glycogen, and fat metabolism in the adaptation on early lactation of dairy cows

During early lactation, high-yielding dairy cows cannot consume enough feed to meet nutrient requirements. As a consequence, animals drop into negative energy balance and mobilize body reserves including muscle protein and glycogen for milk production, direct oxidation, and hepatic gluconeogenesis. To examine which muscle metabolic processes contribute to the adaptation during early lactation, six German Holstein cows were blood sampled and muscle biopsied throughout the periparturient period. From pregnancy to lactation, the free plasma amino acid pattern imbalanced and plasma glucose decreased. Several muscle amino acids, as well as total muscle protein, fat, and glycogen, and the expression of glucose transporter-4 were reduced within the first 4 weeks of lactation. The 2-DE and MALDI-TOF-MS analysis identified 43 differentially expressed muscle protein spots throughout the periparturient period. In early lactation, expression of cytoskeletal proteins and enzymes involved in glycogen synthesis and in the TCA cycle was decreased, whereas proteins related to glycolysis, fatty acid degradation, lactate, and ATP production were increased. On the basis of these results, we propose a model in which the muscle breakdown in early lactation provides substrates for milk production by a decoupled Cori cycle favoring hepatic gluconeogenesis and by interfering with feed intake signaling.     

Estradiol-17β effects on lipid and carbohydrate metabolism and on the induction of a yolk precursor in goldfish,

The effects of estradiol-17β treatment on plasma lipid levels, liver lipid and glycogen reserves were examined during different phases of the reproductive cycle in goldfish, . Estrogen therapy resulted in increased plasma and hepatic lipid levels except during the spawning season. Hepatic glycogen deposits were depleted by estradiol injections during all seasons. Treatment of fish with the estrogen antagonist, CI-628, during the spawning season caused a reduction in plasma and liver lipid levels. Electrophoretic studies conducted during the post-spawning season showed that estrogen induces the appearance of a specific lipoprotein, probably a yolk precursor, in the serum and liver of goldfish.     

应用氧化酶法对高糖高脂动物模型肝糖原含量的测定

目的建立氧化酶法检测肝糖原的方法。方法采用碱中和与缓冲液相配合调节水解液pH至中性,然后用氧化酶法检测肝糖原含量。结果用10μL6mol/LNaOH加入等量肝糖原水解液后,再加入4mLpH7.2磷酸盐缓冲液,可使糖原水解液pH值调为7.2,用于氧化酶法测定糖含量。结论该法操作简便易行,结果稳定、重复性好。     

Seasonal effects of dehydration on glucose mobilization in freeze-tolerant chorus frogs (Pseudacris triseriata) and freeze-intolerant toads (Bufo woodhousii and B. cognatus)

It has been hypothesized that freeze-tolerance in anurans evolved from a predisposition for dehydration tolerance. To test this hypothesis, we dehydrated summer/fall-collected and winter acclimated freeze-tolerant chorus frogs and dehydration-tolerant, but freeze-intolerant, Woodhouse's and Great Plains toads to 25% and 50% body water loss (BWL). Following treatments, we measured glucose, glycogen, and glycogen phosphorylase and glycogen synthetase (summer/fall only) activities in liver and leg muscle. Hepatic glucose levels were not significantly altered by dehydration in either summer/fall-collected frogs or toads. Conversely, winter acclimated frogs did show an increment (2.9-fold) in hepatic glucose with dehydration, accompanied by a reduction in hepatic glycogen levels. Winter acclimated toads did not mobilize hepatic glucose in response to dehydration. Further, hepatic glycogen and phosphorylase activities did not vary in any consistent manner with dehydration in winter toads. Mean leg muscle glucose values were elevated at 50% BWL relative to other treatments, significantly so compared to 25% BWL for summer/fall-collected frogs. The pattern of hepatic glucose mobilization with dehydration in winter frogs is consistent with that in other freeze-tolerant frog species, and provides additional support for the hypothesis that freezing tolerance evolved from a capacity for dehydration tolerance. However, the lack of hepatic glucose mobilization in response to dehydration in fall frogs suggests that a seasonal component to dehydration-induced regulation of glucose metabolism exists in chorus frogs. Furthermore, the absence of a dehydration-induced mobilization of hepatic glucose at both seasons in toads suggests that this dehydration response is not universal for terrestrial anurans.     

Acute inhibition by ethanol of intestinal absorption of glucose and hepatic glycogen synthesis on glucose refeeding after starvation in the rat.

1. Intragastric administration of ethanol (75 mmol/kg body wt.) at 1 h before glucose refeeding of 24 h-starved rats inhibited hepatic glycogen deposition (by 69%) and synthesis (by approx. 70%), but was without significant effect on muscle glycogen deposition and synthesis. 2. Treatment of ethanol-administered rats with methylpyrazole (an inhibitor of alcohol dehydrogenase) did not significantly diminish the inhibitory effect of ethanol on hepatic glycogen deposition after glucose refeeding, suggesting that the inhibition was not dependent on ethanol metabolism. 3. Ethanol delayed and diminished intestinal glucose absorption, at least in part by delaying gastric emptying. 4. At a lower dose (10 mmol/kg body wt.), ethanol inhibited hepatic glycogen repletion and synthesis without compromising intestinal glucose absorption. Ethanol inhibited glycogen deposition (by 40%) in hepatocytes from starved rats provided with glucose + lactate + pyruvate as substrates, consistent with it having a direct effect to diminish hepatic glycogen synthesis by inhibition of gluconeogenic flux at a site(s) between phosphoenolpyruvate and triose phosphate in the pathway. 5. It is concluded that ethanol acutely impairs hepatic glycogen repletion by inhibition at at least two distinct sites, namely (a) intestinal glucose absorption and (b) hepatic gluconeogenic flux.     

Utilization of endogenous reserves and effects of starvation on the health of Prochilodus lineatus (Prochilodontidae)

Prochilodus lineatus Valenciennes (curimbatá) is an important migratory Neotropical fish. It does not feed during spawning migration, and often survives after spawning. The mobilization of energy reserves and some effects of starvation (zero to eight weeks) on fish health were experimentally evaluated. Hepatic glycogen and lipids from the perivisceral fat bodies were the main reserves mobilized during the first four weeks of fasting. During this period, somatic indices and blood parameters showed that fish health was not significantly affected. However, after five weeks of food deprivation, the main energy reserves were depleted and the fish became anaemic. The loss of muscle mass indicates that protein breakdown was an important energy source after the reduction of hepatic and perivisceral reserves. Mortality was increasingly observed from seven weeks of starvation. Prior accumulation of high amounts of reserves is essential to allow movements for long distances during spawning migrations in this species.     

Age-related augmentation of phosphorylase b kinase in hepatic tissue from the glycogen-storage-disease (gsd/gsd) rat.

The effects of food deprivation on body weight, liver weight, hepatic glycogen content, glycogenolytic enzymes and blood metabolites were compared in young and old phosphorylase b kinase-deficient (gsd/gsd) rats. Although the concentration of glycogen in liver from 9-week-old female gsd/gsd rats (730 mumol of glucose equivalents/g wet wt.) was increased by 7-8% during starvation, total hepatic glycogen was decreased by 12% after 24 h without food. In 12-month-old male gsd/gsd rats the concentration of liver glycogen (585 mumol of glucose equiv./g wet wt.) was decreased by 16% and total hepatic glycogen by nearly 40% after food deprivation for 24 h. Phosphorylase b kinase and phosphorylase a were present at approx. 10% of the control activities in 9-week-old gsd/gsd rats, but both enzyme activities were increased more than 3-fold in 12-month-old affected rodents. It is concluded that the age-related ability to mobilize hepatic glycogen appears to result from the augmentation of phosphorylase b kinase during maturation of the gsd/gsd rat.     

Effects of myricetin on glycemia and glycogen metabolism in diabetic rats

In our previous study, we found that myricetin, a naturally occurring bioflavonoid, was able to stimulate glucose transport in rat adipocytes and enhance insulin-stimulated lipogenesis. We report here that after 2 days of treatment with myricetin (3 mg/12 h), hyperglycemia in diabetic rats was reduced by 50% and the hypertriglyceridemia that is often associated with diabetes was normalised. Treatment with myricetin increased hepatic glycogen and glucose-6-phosphate content. It increased hepatic glycogen synthase I activity without having any effect on total glycogen synthase nor phosphorylase a activity. It lowered phosphorylase a activity in the muscle. Thus, the hypoglycemic effect of myricetin is likely to be due to its effect on glycogen metabolism. There was no indication of serious hepatotoxicity with myricetin treatment and therefore, myricetin could be of therapeutic potential in diabetes.     

Heterogeneity of glycogen synthesis upon refeeding following starvation.

1. Starvation of rats for 40 hr decreased the body weight, liver weight and blood glucose concentration. The hepatic and skeletal muscle glycogen concentrations were decreased by 95% (from 410 mumol/g tissue to 16 mumol/g tissue) and 55% (from 40 mumol/g tissue to 18.5 mumol/g tissue), respectively. 2. Fine structural analysis of glycogen purified from the liver and skeletal muscle of starved rats suggested that the glycogenolysis included a lysosomal component, in addition to the conventional phosphorolytic pathway. In support of this the hepatic acid alpha-glucosidase activity increased 1.8-fold following starvation. 3. Refeeding resulted in liver glycogen synthesis at a linear rate of 40 mumol/g tissue per hr over the first 13 hr of refeeding. The hepatic glycogen store were replenished by 8 hr of refeeding, but synthesis continued and the hepatic glycogen content peaked at 24 hr (approximately 670 mumol/g tissue). 4. Refeeding resulted in skeletal muscle glycogen synthesis at an initial rate of 40 mumol/g tissue per hr. The muscle glycogen store was replenished by 30 min of refeeding, but synthesis continued and the glycogen content peaked at 13 hr (approximately 50 mumol/g tissue). 5. Both liver and skeletal muscle glycogen synthesis were inhomogeneous with respect to molecular size; high molecular weight glycogen was initially synthesised at a faster rate than low molecular weight glycogen. These observations support suggestions that there is more than a single site of glycogen synthesis.     

The sequential restoration of plasma metabolite levels,liver composition and liver structure in refed carp,Cyprinus carpio

Effect of realimentation was studied on the structure and function of liver tissue of carp,Cyprinus carpio. Yearling carp, after a 3-month starvation period, were renourished at a feeding rate of 1% body weight per day. Samples were taken at refeeding days 0, 1, 2, 5, 22 and 78. Analyses were made of blood metabolites, liver RNA, DNA, lipids, glycogen and protein and of liver enzyme activities. Additionally, liver cytology was examined by means of qualitative and quantitative electron microscopy. The early refeeding period (up to day 5) was characterized by a fast recovery of plasma metabolite concentrations (protein, total lipids, free fatty acids, glucose), a drastic augmentation of hepatic glycogen reserves, and a pronounced increase of total liver weight and liver-somatic index. Constant values of total hepatic DNA showed that liver weight augmentation was not due to cell proliferation, but to a pronounced enlargement of the existing hepatocytes. Major hunger-related structural modifications of carp hepatocytes such as enlarged mitochondria or prominence of the lysosomal compartment were reversed. A significant volume increase of cell nuclei, together with a particularly strong elevation of hepatic RNA concentrations during initial realimentation suggest an immediate stimulation of protein synthesis. Since the cisternae of the endoplasmic reticulum were not reconstituted during that early phase, protein synthesis may have been executed mainly by free ribosomes. With prolonged realimentation, the volume of the endoplasmic reticulum as well as total and relative contents of liver soluble protein continuously increased, whereas RNA concentrations decreased again. An enforcement of liver oxidative capacity was indicated by the augmentation of cellular number and volume of mitochondria. The activities of the enzymes glucose-6-phosphate dehydrogenase and malic enzyme, which convert excess energy into NADPH, increased steadily. Concomitantly, hepatic lipid accumulation was enhanced. In conclusion, liver metabolism during the early recovery phase seems to be dominated both by repair processes and by intensive protein and glycogen synthesis. The liver slows down these processes during prolonged refeeding and directs an increasing percentage of energy and metabolites toward the generation of reducing equivalents and lipid reserves.Abbreviations BW body weight - ER endoplasmic reticulum - FFA free fatty acids - G6PDH glucose-6-phosphate dehydrogenase - LSI liver somtic index - LW liver weight - ME malic enzyme Presented in part as poster abstract at the International Congress on Research in Aquaculture: Fundamental and Applied Aspects. Antibes, France, 6–10 October, 1991     

Estradiol-17β effects on lipid and carbohydrate metabolism and on the induction of a yolk precursor in goldfish, CarassiusAuratus

The effects of estradiol-17β treatment on plasma lipid levels, liver lipid and glycogen reserves were examined during different phases of the reproductive cycle in goldfish, $\text{Carassius}$$\text{auratus}$. Estrogen therapy resulted in increased plasma and hepatic lipid levels except during the spawning season. Hepatic glycogen deposits were depleted by estradiol injections during all seasons. Treatment of fish with the estrogen antagonist, CI-628, during the spawning season caused a reduction in plasma and liver lipid levels. Electrophoretic studies conducted during the post-spawning season showed that estrogen induces the appearance of a specific lipoprotein, probably a yolk precursor, in the serum and liver of goldfish.     

Short-term effects of thalidomide analogs on hepatic glycogen and nitric oxide in endotoxin-challenged rats

Hepatic glycogen metabolism is altered by nitric oxide (NO) during endotoxic shock. Thalidomide analogs immunomodulate the endotoxin-induced cytokines which regulate the NO release. We analyzed the short-term effects of some thalidomide analogs on the hepatic glycogen store and on the plasma and hepatic NO in an acute model of endotoxic challenge in rat. An endotoxin dose selection was performed. Rats received vehicle, thalidomide or analogs orally and, two hours after last dose, they were injected with endotoxin (5 mg/kg). Animals were sacrificed 2 h after challenge. Liver glycogen was quantified by the anthrone technique. Plasma and hepatic NO was determined by Griess reagent and HPLC. Hepatic interferon-gamma, a NO co-inducer, was measured by ELISA. Endotoxin caused inverse dose-dependent effects on plasma NO and on glycogen.Thalidomide analogs showed short-term regulatory effects on glycogen, some of them increased it. Plasma NO was almost unaffected by analogs but hepatic NO was strikingly modulated. Analogs slightly up-regulated the liver interferon-gamma and two of them increased it significantly. Thalidomide analogs may be used as a pharmacological tool due to their short-term regulatory effects on glycogen and NO during endotoxic shock. Drugs that increase glycogen may improve liver injury in early sepsis.     

Hepatic morphological alterations,glycogen content and cytochrome P450 activities in rats treated chronically with N<Superscript>ω</Superscript>-nitro-L-arginine methyl ester (L-NAME)

Chronic treatment of rats with N(omega)-nitro-L-arginine methyl ester (L-NAME), an inhibitor of nitric oxide (NO) biosynthesis, results in hypertension mediated partly by enhanced angiotensin-I-converting enzyme (ACE) activity. We examined the influence of L-NAME on rat liver morphology, on hepatic glycogen, cholesterol, and triglyceride content, and on the activities of the cytochrome P450 isoforms CYP1A1/2, CYP2B1/2, CYP2C11, and CYP2E1. Male Wistar rats were treated with L-NAME (20 mg/rat per day via drinking water) for 2, 4, and 8 weeks, and their livers were then removed for analysis. Enzymatic induction was produced by treating rats with phenobarbital (to induce CYP2B1/2), beta-naphthoflavone (to induce CYP1A1/2), or pyrazole (to induce CYP2E1). L-NAME significantly elevated blood pressure; this was reversed by concomitant treatment with enalapril (ACE inhibitor) or losartan (angiotensin II AT(1) receptor antagonist). L-NAME caused vascular hypertrophy in hepatic arteries, with perivascular and interstitial fibrosis involving collagen deposition. Hepatic glycogen content also significantly increased. L-NAME did not affect fasting glucose levels but significantly reduced insulin levels and increased the insulin sensitivity of rats, based on an intraperitoneal glucose tolerance test. Immunoblotting experiments indicated enhanced phosphorylation of protein kinase B and of glycogen synthase kinase 3. All these changes were reversed by concomitant treatment with enalapril or losartan. L-NAME had no effect on hepatic cholesterol or triglyceride content or on the basal or drug-induced activities and protein expression of the cytochrome P450 isoforms. Thus, the chronic inhibition of NO biosynthesis produced hepatic morphological alterations and changes in glycogen metabolism mediated by the renin-angiotensin system. The increase in hepatic glycogen content probably resulted from enhanced glycogen synthase activity following the inhibition of glycogen synthase kinase 3 by phosphorylation.     

Transforming growth factor alpha inhibits glycogen synthesis and counteracts the stimulation by insulin in hepatocytes.

Rat transforming growth factor alpha (TGF alpha) inhibits glycogen synthesis in rat and guinea pig hepatocyte cultures and counteracts the stimulation of glycogen deposition and activation of glycogen synthase caused by insulin. The EC50 for inhibition of glycogen deposition was 0.2nM. The inhibition of glycogen synthesis was also observed in the absence of extracellular Ca2+ and was not blocked by indomethacin, suggesting that it is not mediated by production of prostaglandins. Since TGF alpha is produced by hepatocytes during liver regeneration and by macrophages during endotoxin stimulation, it may have an autocrine/paracrine effect on hepatic carbohydrate metabolism in these states, and may account for the low hepatic glycogen levels during liver regeneration and the impaired glucose tolerance associated with sepsis.     

Seasonal changes in lipid composition and glycogen storage associated with freeze-tolerance of the earthworm, Dendrobaena octaedra

The earthworm, Dendrobaena octaedra, is a common species in the uppermost soil and humus layers of coniferous forests and tundra in temperate and subarctic regions. The species is freeze-tolerant and may survive several months in a frozen state. Upon freezing, glycogen reserves are rapidly converted to glucose serving as a cryoprotectant and fuel for metabolism. In the present study we investigated the induction of freeze-tolerance under field conditions, and sought to find relationships between temperature, glycogen and fat reserves, membrane phospholipid composition and the degree of freeze-tolerance. Freeze-tolerance was induced when worms had experienced temperatures below 5°C for 2 weeks or more. Freeze-tolerance was linked to the magnitude of glycogen reserves, which also fluctuated with field temperatures being highest in autumn and winter. On the other hand fat reserves seemed not to be linked with freeze-tolerance at all. However, high glycogen alone did not confer freeze-tolerance; alterations in the membrane phospholipid fatty acid composition (PLFA) were also necessary in order to secure freeze-tolerance. The changes in PLFA composition were generally similar to changes occurring in other ectothermic animals during winter acclimation with an increased degree of unsaturation of the PLFAs.     

Sleep deprivation decreases glycogen in the cerebellum but not in the cortex of young rats

We tested whether brain glycogen reserves were depleted by sleep deprivation (SD) in Long-Evans rats 20-59 days old. Animals were sleep deprived beginning at lights on and then immediately killed by microwave irradiation. Glycogen and glucose levels were measured by a fluorescence enzymatic assay. In all age groups, SD reduced cerebellar glycogen levels by an average of 26% after 6 h of SD. No changes were observed in the cortex after 6 h of SD, but in the oldest animals, 12 h of SD increased cortical glycogen levels. There was a developmental increase in basal glycogen levels in both the cortex and cerebellum that peaked at 34 days and declined thereafter. Robust differences in cortical and cerebellar glycogen levels in response to enforced waking may reflect regional differences in energy utilization and regulation during wakefulness. These results show that brain glycogen reserves are sensitive to SD.