Total Body Glycogen Research Articles

Impaired Glucose Tolerance and Predisposition to the Fasted State in Liver Glycogen Synthase Knock-out Mice

Conversion to glycogen is a major fate of ingested glucose in the body. A rate-limiting enzyme in the synthesis of glycogen is glycogen synthase encoded by two genes, GYS1, expressed in muscle and other tissues, and GYS2, primarily expressed in liver (liver glycogen synthase). Defects in GYS2 cause the inherited monogenic disease glycogen storage disease 0. We have generated mice with a liver-specific disruption of the Gys2 gene (liver glycogen synthase knock-out (LGSKO) mice), using Lox-P/Cre technology. Conditional mice carrying floxed Gys2 were crossed with mice expressing Cre recombinase under the albumin promoter. The resulting LGSKO mice are viable, develop liver glycogen synthase deficiency, and have a 95% reduction in fed liver glycogen content. They have mild hypoglycemia but dispose glucose less well in a glucose tolerance test. Fed, LGSKO mice also have a reduced capacity for exhaustive exercise compared with mice carrying floxed alleles, but the difference disappears after an overnight fast. Upon fasting, LGSKO mice reach within 4 h decreased blood glucose levels attained by control floxed mice only after 24 h of food deprivation. The LGSKO mice maintain this low blood glucose for at least 24 h. Basal gluconeogenesis is increased in LGSKO mice, and insulin suppression of endogenous glucose production is impaired as assessed by euglycemic-hyperinsulinemic clamp. This observation correlates with an increase in the liver gluconeogenic enzyme phosphoenolpyruvate carboxykinase expression and activity. This mouse model mimics the pathophysiology of glycogen storage disease 0 patients and highlights the importance of liver glycogen stores in whole body glucose homeostasis.

Components of energy expenditure in patients with severe sepsis and major trauma: a basis for clinical care.

To obtain accurate values for the components of energy expenditure in critically ill patients with sepsis or trauma during the first 2 wks after admission to the intensive care unit. Prospective study. Critical care unit and university department of surgery in a single tertiary care center. Twelve severely septic (median Acute Physiology and Chronic Health Evaluation II Score, 23; range, 15 to 34) and 12 major trauma patients (median Injury Severity Score, 33.5; range, 26 to 50). Total body fat, total body protein, and total body glycogen were measured as soon as hemodynamic stability had been reached and repeated 5 and 10 days later. Resting energy expenditure (REE) was measured daily by indirect calorimetry. Changes in total body fat, total body protein, and total body glycogen in critically ill patients provide data for the accurate construction of an energy balance. Energy intake minus energy balance gives a direct measurement of total energy expenditure (TEE) and, when combined with measurements of REE, activity energy expenditure can be obtained. TEE, REE, and activity energy expenditure were calculated for two sequential 5-day study periods. REE progressively increased during the first week after the onset of severe sepsis or major trauma, peaking during the second week at 37 +/- 6% (SEM) and 60 +/- 13% greater than predicted, respectively. For both the sepsis and trauma patients, TEE was significantly higher during the second week than during the first week (3257 +/- 370 vs. 1927 +/- 370 kcal/day, p < .05, in sepsis; 4123 +/- 518 vs. 2380 +/- 422 kcal/day, p < .05, in trauma). During the first week after admission to the hospital, TEE in sepsis and trauma patients, respectively, averaged 25 +/- 5 and 31 +/- 6 kcal/kg of body weight/day, and during the second week, 47 +/- 6 and 59 +/- 7 kcal/kg/day (p < .03, for comparison of first and second weeks). For the first week, the ratio of TEE to REE was 1.0 +/- 0.2 and 1.1 +/- 0.2 but during the second week rose to 1.7 +/- 0.2 and 1.8 +/- 0.2 in patients with sepsis (p < .05, for comparison of weeks) and trauma (p = .09), respectively. Total energy expenditure is maximal during the second week after admission to the critical care unit, reaching 50 to 60 kcal/kg/day.

Glycogen storage in normal and wing-mutant strains of Drosophila melanogaster

Total body weight, total glycogen content and the percentage of body weight attributable to stored glycogen were measured in wild-type and two wing-mutant strains of 0–2-day-old (immature) and 5–7-day-old (mature) Drosophila melanogaster. Wild-type and wing mutant strains did not differ significantly in any of the measured parameters at 0–2 days of age. By 5–7 days of age, significant increases in glycogen content and glycogen percent had occurred in both wild-type and wing-mutant strains. Likewise, by 5–7 days of age, total body weight had increased significantly in the mature wild-type and vestigial strains but not in apterous flies. Mature wild-type flies displayed significantly greater total body glycogen content and glycogen percent when compared with the mature apterous and vestigial wing-mutant strains.

The apparent absence of a homeostatic hypotrehalosaemic hormone in the German cockroach ( Blattella germanica)

The possible existence of a homeostatic hypotrehalosaemic hormone in the German cockroach was investigated using a trehalose tolerance test. After injection of 450 μg trehalose into the haemolymph, concentrations of trehalose almost tripled and were much higher than ever found in normal animals. The decrease of these artificially raised haemolymph levels was temperature dependent and very slow; 8 h after injection, haemolymph trehalose levels were still markedly elevated. In the trehalose tolerance test the changes in total body glycogen per μg/μl change in haemolymph trehalose were much smaller than induced by the purified Blattella hypertrehalosaemic factor. This suggests, that it is unlikely that the German cockroach possesses a homeostatic hypotrehalosaemic hormone.

EFFECTS OF DIFLUBENZURON ON LARVAL DEVELOPMENT OF ZAPRINONUS PARAVITTIGER (GODBLE AND VAIDYA) (DIPTERA: DROSOPHILIDAE)

Feeding of diflubenzuron to different-aged larvae of banana fruitfly, Zaprionus paravittiger (Godble and Vaidya), produced a differential susceptibility. The first-instar larvae were significantly more susceptible than the second- and third-instar larvae. The ID 50 (50% inhibitory dose) values for adult emergence were 0.16, 0.32 and 0.95 ppm for first-, second-, and third-instar larvae, respectively. The frequency of morphological abnormalities increased and F1 adults failed to reproduce. Furthermore, the total body glycogen increased and total body proteins decreased after feeding diflubenzuron to second-instar larvae for 24 h.

Altered Carbohydrate Levels and Gluconeogenic Enzyme Activity in Trichoplusia ni Parasitized by the Insect Parasite, Hyposoter exiguae

The association of the insect parasite, Hyposoter exiguae, with its host, Trichoplusia ni, was characterized by increased host hemolymph sugar and fat body glycogen levels. Elevation of these carbohydrate reserves was accompanied by an increase in the maximal activity of fructose 1,6 bisphosphatase in the fat body. The latter result suggests that an increase in gluconeogenic flux through the fructose 6 phosphate-fructose 1,6 bisphosphate substrate cycle may occur in parasitized insects. Moreover, the maximum rate of cycling may be increased in parasitized tissue as suggested by alteration in the maximal activity of phosphofructokinase. The above effect on fructose 1,6 bisphosphatase could not be explained on the basis of alterations in adenylate nucleotide levels and positive substrate crossover was not observed. The results indicate that the normal metabolic regulation of carbohydrate synthesis may be upset in parasitized individuals. Altered tissue carbohydrate levels are commonly observed during parasitic infections involving invertebrate hosts and metazoan parasites. Although the specific nature of such changes is variable, depletion of carbohydrate reserves is commonly observed. Gordon et al. (1971) reported decreased fat body glycogen levels in Schistocerca gregaria infected by the nematode Mermis nigrescens, and Rutherford and Webster (1978) later observed depressed hemolymph trehalose concentrations. Lowered host blood sugar and glycogen reserves also characterized the associations of the schistosomes, Schistosoma mansoni and S. haematobium with their snail hosts, Biomphalaria alexandrina and Bulinus truncatus, respectively (Ishak et al., 1975). The metabolic basis for glycogen depletion in B. glabrata infected with S. mansoni was recently established by Schwartz and Carter (1982), who demonstrated elevated glycogen phosphorylase activity in infected hosts. In contrast to the above studies, Manohar and Venkateswaro Rao (1976) reported elevated blood sugar in the snail Lymnaea luteola following infection by the trematode, Prosthogonimus sp., and later concluded that gluconeogenesis was responsible (Manohar and Venkateswaro Rao, 1977a, 1977b). Changes in tissue carbohydrate levels also occur during the host associations of hymenopterous insect parasites. Dahlman (1975) reported that hemolymph trehalose concentrations deReceived 6 January 1984; revised 27 February 1984; accepted 27 February 1984. creased in Manduca sexta parasitized by Apanteles congregatus. Trehalose concentrations in Heliothis virescens parasitized by Microplitis croceipes, however, were markedly elevated (Dahlman and Vinson, 1975). Moreover, fat body glycogen levels were increased during the course of infection although total body glycogen decreased (Dahlman and Vinson, 1980). Those authors suggested that fat body glycogen was the source of the elevated hemolymph trehalose. Elevated host hemolymph trehalose and fat body glycogen concentrations were also reported in Trichoplusia ni (Hiibner) (Noctuidae) parasitized by Hyposoter exiguae (Viereck) (Ichneumonidae) (Thompson, 1982); preliminary assay of glycogen phosphorylase activity indicated very low levels in both control and parasitized individuals (Thompson, unpublished observations). Moreover, previous studies on nutritional physiology demonstrated that parasitized hosts have substantially lowered efficiencies of food conversion (Thompson, 1983). It is suggested, therefore, that increased gluconeogenesis may be responsible for the elevated carbohydrate reserves of parasitized Trichoplusia ni. The present investigation was carried out to test that hypothesis by examining the enzymes of the fructose 6 phosphate (F6P)-fructose 1,6 bisphosphate (FBP) substrate cycle. Specifically, the activities of phosphofructokinase (PFKase) and fructose 1,6 bisphosphatase (FBPase), 2 rate-controlling enzymes affecting the net flux through the glycolytic and gluconeogenic pathways, were determined in the fat body of parasitized fourth instar T. ni

The effect of naphthalene on oxygen consumption and hemoglobin concentration in Chironomus attenuatus and on oxygen consumption and life cycle of Tanytarsus dissimilis

AbstractThe effects of naphthalene on the physiology and life cycle of two species of benthic macroinvertebrates, Chironomus attenuatus and Tanytarsus dissimilis (Diptera: Chironomidae), were determined. The acute effects measured were survival, oxygen consumption, hemoglobin concentration and total body glycogen content. A flow‐through system was used to determine chronic effects on life cycle and reproduction parameters.Both species had LC50 values of approximately 13 mg/L. After exposure to naphthalene for 1 h, the oxygen consumption of both species decreased. Tanytarsus was more sensitive than Chironomus, which is consistent with the life histories of the two species. The decrease in oxygen uptake was due to inhibition of the electron transport chain or interference with functioning of the nervous system.Hemoglobin concentrations in Chironomus were not good indicators of naphthalene stress. Although hemoglobin in Chironomus decreased after 4 h of exposure, the decrease was not significant. The decrease could not be accounted for by alteration of hemoglobin structure or by inhibition of synthesis.Life cycle exposures at naphthalene concentrations of less than 0.5 mg/L resulted in minimal effects. Egg hatching and adult emergence were the best indicators of chronic exposure. Pupation times and numbers of eggs were not significantly changed.

Effects of the insect parasite, Hyposoter exiguae on the total body glycogen and lipid levels of its host, Trichoplusia ni

1. 1. Parasitization of late 3rd instar Trichoplusia ni by Hyposoter exiguae resulted in a marked reduction in weight gain as well as delayed development. Similar effects were observed in partially starved larvae reared on nutrient deficient media. 2. 2. The total body lipid concentration and level in T. ni larvae were reduced following parasitization or starvation. 3. 3. The total body glycogen concentration and level in T. ni larvae were also reduced as a result of starvation. Parasitized individuals, however, had glycogen concentrations similar to control unparasitized larvae, but their small size reduced the total level considerably. 4. 4. The reduction of total body glycogen and lipid reserves in parasitized T. ni appeared to occur in a similar fashion to that which results from partial starvation, suggesting that these effects of parasitization may result from the competition between the developing parasite and host tissues for available nutrients.

Compartment a1 and semicompartmental approaches for measuring glucose carbon flux to fatty acids and other products in vivo

We have attempted to estimate the flux of glucose carbon to total body fatty acids and to other metabolic end products in Bar Harbor 129/J mice fasted 5-8 hr. Tracer [U-(14)C]glucose was injected intravenously, and the following data were obtained at various times up to 180 min: plasma glucose C specific activity, plasma glucose concentration, total body glycogen, and (14)C in total body fatty acid, total body lipid, unsaponifiable lipid, expired CO(2), and in hepatic and extrahepatic glycogen. The data were analyzed by three techniques, namely, multicompartmental, semicompartmental, and noncompartmental analyses. All three methods yielded comparable rates of glucose C conversion to total body fatty acids (2-3 micro g of glucose C/min/20 g of body weight). Although the semicompartmental approach is extremely simple (it only requires analyses of plasma glucose specific activity as a function of time and (14)C-labeled fatty acid at one point in time), it gives an apparently valid approximation for the flux of glucose C to fatty acids. Other quantitative aspects of glucose metabolism in postabsorptive mice are also considered.

The role of stored glycogen during long-term temperature acclimation in the freshwater crayfish, Orconectes virilis

1. 1. Glycogen content of heart, abdominal muscle and hepatopancreas was measured in starved crayfish, Orconectes virilis, acclimated at 1–2°C and 21°C for 45 days. 2. 2. The average percentages of glycogen in heart, hepatopancreas and abdominal muscle were observed to be 2·90, 0·70 and 0·18 per cent in 1–2°C acclimated crayfish, and 1·57, 0·62 and 0·051 per cent in 21°C acclimated crayfish. 3. 3. Changes in total body glycogen could account for only 1 per cent of the differential respiratory rate associated with metabolic temperature adaptation. 4. 4. Changes in glycogen content of heart muscle could account for 36–42 per cent of the differential respiratory rate associated with metabolic temperature adaptation.

THE EFFECT OF PITUITARY PREPARATIONS ON THE TOTAL BODY GLYCOGEN, WATER, NITROGEN AND FAT OF MICE

NUMEROUS INVESTIGATIONS have been undertaken to elucidate the relation of the pituitary body to the metabolism of carbohydrates, proteins and fats. Recently we reported on the effect of various pituitary preparations on the ketonuria and total body fat of normal fasted mice (i). In order to obtain information of a wider scope regarding the metabolic changes induced by pituitary preparations, this study has been extended to include changes in total body glycogen, water and nitrogen. The studies reported, with the exception of the antidiuretic potency of extracts, were carried out on 5 to 6-week-old female mice of a pure strain (dba) and weighing from 10 to 13 gm. The antidiuretic potency was estimated in male hooded rats 8 weeks old by the method previously described by Burn (2).