Insulin-like growth factor 2 and the insulin receptor, but not insulin, regulate fetal hepatic glycogen synthesis

Whether insulin or IGFs regulate glycogen synthesis in the fetal liver remains to be determined. In this study, we used several knockout mouse strains, including those lacking Pdx-1 (pancreatic duodenal homeobox-1), Insr (insulin receptor), and Igf2 (IGF-II) to determine the role of these genes in the regulation of fetal hepatic glycogen synthesis. Our data show that insulin deficiency does not alter hepatic glycogen stores, whereas Insr and Igf2 deficiency do. We found that both insulin receptor isoforms (IR-A and IR-B) are present in the fetal liver, and their expression is gestationally regulated. IR-B is highly expressed in the fetal liver; nonetheless, the percentage of hepatic IR-A isoform, which binds Igf2, was significantly higher in the fetus than the adult. In vitro experiments demonstrate that Igf2 increases phosphorylation of hepatic Insr, insulin receptor substrate-2, and Akt proteins and also the activity of glycogen synthase. Igf2 ultimately increased glycogen synthesis in fetal hepatocytes. This increase could be blocked by the phosphoinositide 3-kinase inhibitor LY294008. Taken together, we propose Igf2 as a major regulator of fetal hepatic glycogen metabolism, the insulin receptor as its target receptor, and phosphoinositide 3-kinase as the signaling pathway leading to glycogen formation in the fetal liver.

Glabridin from Chinese herb licorice inhibits fatigue in mice

The inhibiting effect of glabridin from Chinese herb Licorice on fatigue was investigated in male BALB/c mice. Mice were divided into the following 4 experimental groups: control group (CG), low dose group (LG), middle dose group (MG) and high dose group (HG,). The control group was given 0.5% Tween 80 solution and the treatment groups (LG, MG, HG) were given various doses of glabridin (5, 10, 20 mg/kg) for 28 consecutive days. Body mass, blood lactic acid (BLA), serum blood urea nitrogen (BUN), liver glycogen and muscle glycogen concentrations in mice were determined. Results showed that glabridin significantly inhibited fatigue, which extended the exhaustive exercise time of mice, effectively delayed the elevation of blood lactic acid and increase in the storage of liver and muscle glycogen.

Maternal low protein diet restricted to the preimplantation period induces a gender-specific change on hepatic gene expression in rat fetuses

It has been shown previously that maternal low protein diet (LPD) throughout rat gestation altered hepatic gene expression and enzyme activities in offspring. Here, we investigate the effect of maternal LPD (9% casein vs. 18% control) exclusively during the preimplantation period (switched diet group) or provided throughout gestation on hepatic gene expression in day 20 fetuses. Using quantitative competitive PCR, we found that switched diet induced a two-fold increase (P = 0.008) in hepatic gene expression of phosphoenolpyruvate carboxykinase (PEPCK, a rate limiting enzyme for gluconeogenesis) in male fetuses and a 17% increase (P = 0.005) in 11beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1, acts primarily as a reductase to produce active glucocorticoid) in female liver compared with control fetuses. Maternal LPD administered throughout gestation increased 11beta-HSD1 expression in male fetal liver by 27% (P = 0.042) compared with controls. However, maternal LPD fed for either period did not affect fetal hepatic insulin receptor (IR), glucocorticoid receptor (GR), glycogen synthase (GS) nor placental glucose transporter 1 (Glut1) and 3 (Glut3) transcript levels. The alteration in fetal hepatic gene expression could not be attributed specifically to known regulators including insulin or glucose concentrations in fetal blood nor alteration in cAMP in fetal liver, although a combination of these regulatory factors may be responsible. Fetal hepatic glycogen level was unaffected by maternal diet. The present findings show that the long term potential of the preimplantation embryo is sensitive to maternal LPD such that basal levels of hepatic gene expression in day 20 fetuses are altered in a gender-specific manner.

Anti-fatigue activity of a triterpenoid-rich extract from Chinese bamboo shavings (Caulis bamfusaein taeniam)

The anti-fatigue activity of a pentacyclic triterpenoid extract from bamboo shavings (EBS) from the bark of bamboo (Bambusa tuldoides Munro), was evaluated in BALB/c mice. EBS, isolated by the supercritical CO(2) fluid extraction (SFE) technique, was given to mice at concentrations of 0.04 (low-dose group), 0.08 (middle-dose group) and 0.25 g/kg body weight (high-dose group). The anti-fatigue activity of EBS was estimated by the change in body weight, weight-loaded swimming test and climbing test, and corresponding parameters including serum urea nitrogen, hepatic glycogen and blood lactic acid were measured. The results showed that an appropriate level of EBS could prolong the weight-loaded swimming and climbing time, and had an active effect on the serum urea nitrogen, hepatic glycogen and blood lactic acid level in BALB/c mice, which significantly embodied the anti-fatigue activity of EBS. Overall, it is predicted that EBS, being a composition mainly containing a group of pentacyclic triterpenoids, and its main triterpenoid components have great potential for application in relevant fields for its anti-fatigue activity.

Effects of the antithyroid agent propylthiouracil in a partial life cycle assay with zebrafish

Some ubiquitous pollutants of the aquatic environment, such as PCBs or other polyhalogenated aromatic hydrocarbons, may disrupt the thyroid hormone system. In a partial life cycle assay with zebrafish (Danio rerio), we studied the effects of the reference compound propylthiouracil (PTU) on reproduction, growth and development, histopathology of some target tissues, and plasma thyroid hormone levels. PTU induced a concentration-dependent increase of egg production with a concomitant decrease of mature oocyte size but had no effect on fertilization rate or hatching. In F1, serious dysmorphogenesis was found in 4 dph larvae at the highest PTU level tested (100 mg/L), and there was a dose-dependent decrease in body length and weight at 42 dph (significant at 100 mg/L PTU). At this time, there was also a decreased scale thickness, suggesting inhibited metamorphosis, detectable at 1 mg/L PTU and higher. PTU also induced activation of the thyroid follicles in a concentration-dependent way, in juveniles associated with hyperemia in the thyroid area, and depletion of liver glycogen. Effects in adults were associated with decreased circulating levels of the thyroid hormones T3 and T4. These observations indicate that disruption of the thyroid hormone system may affect the fitness of these aquatic organisms. The zebrafish model may contribute to the identification of thyroid hormone disrupting activity in water samples and also in the interpretation of histological observations in free-ranging fish species.

Effects of inducing physiological hyperglucagonemia on metabolic responses to exercise

The purpose of the present study was to assess the effects of exogenously increasing the circulating levels of glucagon on the metabolic responses to exercise in rats. A total of six groups of rats were infused (iv) either with glucagon (20 or 50 ng x kg(-1) x min(-1)) or saline (0.9% NaCl), either in the resting state or during a bout of running exercise (45 min, 26 m x min(-1), 0% grade). Blood samples were taken at the end of the 45-min experiment. Animals infused with glucagon at 50 ng x kg(-1) x min(-1) showed significantly (P<0.01) higher mean plasma glucagon concentrations than animals infused with saline or glucagon at 20 ng x kg(-1) x min(-1). In addition, exercise resulted in significantly (P<0.05) higher mean plasma glucagon concentrations, compared to rest, in all groups. In spite of these differences in glucagon concentrations, there were no significant (P>0.05) effects of exercise and glucagon infusion on mean hepatic glycogen, plasma glucose, insulin, C-peptide, beta-hydroxybutyrate, or catecholamine concentrations. Although exercise resulted in a significant (P<0.01) increase in plasma glycerol and free fatty acid concentrations and a significant (P<0.05) decrease in glycogen in the soleus muscle, these responses were not affected by the glucagon infusion. These results suggest that the liver is non-responsive to physiological hyperglucagonemia in a short-term (45 min) exercise situation.

[Cryopreserved substance, isolated from human fetal liver, restore biochemical processes in acute liver failure]

Recovery processes dynamics in liver when treating experimental acute hepatic insufficiency (AHI) of various etiology by using cryopreserved biopreparations, obtained from human embryo liver of different terms of development (10-12 weeks), human fetuses (22-24 week of development).

Adrenomedullar catecholamine liberation and carbohydrate metabolism during the first 30 min of an aggressive encounter in rats

The correlation between adrenomedullar catecholamine secretion and metabolic events was investigated in previously isolated fighting male rats. Aggressive encounters were stopped before the apparition of a dominance order. Aggression consisted of short bursts of reciprocal bites, threatening behavior, and short pauses intercalated. After 30 min of fighting, the percent of catecholamine-stained adrenomedullar cells was reduced significantly in fighters. Fighters showed a significant reduction in liver glycogen, while their blood glucose was increased. Muscle-free glucose showed no statistically significant changes compared to controls, while muscle glucose consumption increased. In the muscle of fighting rats, glycogen content was decreased. Our results demonstrated that there is an adrenomedullar activation in early stages of aggression, the changes in carbohydrate metabolism being in correlation with the catecholamine activation.

Different effects of subcutaneous D,L-3-hydroxybutyrate and acetoacetate injections on food intake in rats

Cumulative food intake following subcutaneous injection of D,L-3-hydroxybutyrate (DL3HB) or acetoacetate (AcAc) was investigated in rats, because ketone bodies might contribute to food intake regulation according to Kennedy's lipostatic hypothesis. In addition, the metabolic effects of DL3HB-injections were studied by measuring the levels of plasma D3HB, plasma non-esterified fatty acids (NEFA), plasma glycerol, blood glucose, and liver glycogen. Subcutaneously injected DL3HB (10 mmoles/kg body weight) significantly reduced feeding while equimolar AcAc did not. DL3HB-injection increased plasma D3HB and decreased plasma NEFA and plasma glycerol 1-2 hours after the injection but did not affect blood glucose or liver glycogen content. The data suggest that oxidation of D3HB to AcAc contributes to the inhibition of feeding following subcutaneous DL3HB-injection in rats.

Chronic valproate administration reduces fasting ketonemia in children

We previously found that chronic administration of sodium valproate to suckling infant mice reduced plasma beta-hydroxybutyrate levels but had no effect on plasma free fatty acid or glycerol concentrations. We now report that valproate has a similar effect in children taking the drug for epilepsy. In larger doses, valproate also depleted the infant mouse liver glycogen content. These findings may relate to the hepatic toxicity of valproate. We advise caution if the drug is being considered for use in chronically malnourished children or when the caloric intake of normal children is likely to be reduced during periods of acute illness.

Subcellular responses of hepatocytes to diabetes in control-fed rats

The biochemistry and ultrastructure of hepatocytes from streptozotocin-diabetic rats adapted to a controlled feeding schedule are described. The microsomal enzyme glucose-6-phosphatase (G-6-Pase), required for glucose release from the hepatocyte was monitored in homogenate preparations at times after the initiation of feeding in rats trained to a 6 h feeding, 18 h fasting cycle. G-6-Pase specific activity which is increased in ad lib fed diabetic rats was not further increased with time after the initiation of feeding in the feeding trained animals. However, the known elevation in G-6-Pase latent activity of the diabetic rat was reduced during the feeding cycle of times of minimum and maximum plasma glucose. Enzyme latency is a reflection of the multicomponent nature of G-6-Pase activity; therefore, plasma glucose levels may influence elements of that multicomponent system. Hepatic rough and smooth endoplasmic reticulum (RER + SER) fractions from the diabetic animals exhibited high and equivalent G-6-Pase specific activities independent of feeding or fasting. Ultrastructural observations of periportal hepatocytes showed a high content of SER correlated with the high G-6-Pase specific activity and closely associated with dispersed particles of glycogen at all times after the initiation of feeding. Also, an increase in SER was observed in the fasted normal animals although particulate glycogen was nearly absent. These findings support earlier work indicating that diabetes stimulates the proliferation of hepatic SER and that the membranes of this organelle are altered from those of the normal animal.

Dietary fat and exercise conditioning effect on metabolic parameters in the horse

Four isocaloric diets containing 4, 8, 12 and 16% dietary fat (as soybean oil) were fed to four horses at four intervals according to a Latin square design. After 3 weeks of conditioning at each interval, diet effects were evaluated by trotting all horses at 3.2 m/sec for 6 hours. Pre- and posttrotting responses were measured in muscle and liver glycogen, serum long-chain fatty acids, serum electrolytes, serum enzymes, serum cholesterol, plasma glucose, packed cell volume and hemoglobin. Dietary fat was highly correlated with exercise-induced plasma glucose changes and with cholesterol concentrations. Regardless of the diet, linoleate concentration was about eight times higher than that of the other fatty acids, and it increased slightly as dietary fat levels increased. Stearate concentration also increased with increasing dietary fat but palmitic and oleic acid decreased. Increases in fat intake also resulted in slight increases in liver glycogen at the resting level. Conditioning resulted in a significant decrease in exercise-induced fluctuations of serum enzymes and electrolytes but significantly increased elevations of plasma long-chain fatty acid concentrations. Resting muscle glycogen increased by 37% during the study as a result of conditioning, but there was no effect on liver glycogen at rest or after exercise. Feeding of the four levels of dietary fat in the form of soybean oil had no adverse effects and proved a safe and efficient method of providing concentrated energy to working horses.

The modifying effect of nutritional intake of the posttraumatic depletion in hepatic glycogen in rats

Hepatic glycogen levels were measured in rats both on oral food ad libitum and where intravenous nutrition was supplied at 0.1, 0.2, and 0.35 Kcal/gm of body weigh/day at 24 and 72 hours after injury. While on oral food rats with a closed femoral fracture had a lower level (25 +/- 6.5 mg/gm of liver) than normal (66 +/- 9.1 mg/gm of liver, P less than 0.005), 24 hours after injury. There was a corresponding rise in blood sugar (161 +/- 20 leads to 240 +/- 23 mg/100 ml, P less than 0.005) at 24 hours. However the food intake fell (23.8 +/- 1.5 leads to 16.6 +/- 2.4 gm/day, P less than 0.01) during the first 24 hours after the injury. When intravenous nutrition was given at a caloric level of 0.35 Kcal/gm/day, hepatic glycogen levels were above normal and there was no difference between injured and noninjured animals. At 0.2 Kcal/gm/day there was also no difference between injured and noninjured animals, but glycogen levels fell from norman levels (78 +/- 12.9 mg/gm) to lower levels (33 +/- 11.9 mg/gm, P less than 0.01) over the 24-hour to 72-hour period. Low levels of caloric intake (0.1 Kcal/gm/day) resulted in a fall in glycogen level in both injured and noninjured animals, with the decrease being significantly greater in the injured animals. It is concluded that maintenance of the caloric intake of rats at normal or high levels via the intravenous route can prevent the depletion of hepatic glycogen produced by a femoral fracture.

Carbohydrate metabolism in the fetal pig during late gestation

In acute experiments on pregnant sows under sodium pentobarbitone anaesthesia, acid base balance, oxygenation and plasma metabolite concentrations were well maintained in the dam and all fetuses which remained undisturbed in utero, irrespective of the duration of the experiment. Fetal liver glycogen concentrations were also unaffected by the time of removal of the fetus. By contrast, intravascular catheterization and withdrawal of blood led to fetal hyperglycaemia and depletion of hepatic glycogen although blood gas and pH values were not changed by these procedures. In the 1 1/2--2 h sampling period following catheterization the normal positive umbilical venous-arterial differences in plasma glucose and lactate generally became reversed. These changes were prevented by the administration of hexamethonium (10--15 mg . kg-1 i.v.) but the drug did not block the fall in hepatic glycogen in catheterized fetuses. Both adrenaline and noradrenaline, which were each infused intravenously at 2.7--3.9 or 0.6--0.9 microgram . kg-1 . min-1, resulted in fetal hyperglycaemia and lacticacidemia together with a fall in arterial blood pH; hepatic glycogen concentrations in these fetuses were also reduced. The apparent sensitivity of the glycogenolytic mechanism to surgical trauma and haemorrhage in the fetal piglet is discussed in relation to findings in other species.

Lak of influence of glucagon on glucose homeostasis after prolonged exercise in rats

The significance of glucagon for post-exercise glucose homeostasis has been studied in rats fasted overnight. Immediately after exhaustive swimming either rabbit-antiglucagon serum or normal rabbit serum was injected by cardiac puncture. Cardiac blood and samples of liver and muscle tissue were collected before exercise and repeatedly during a 120 min recovery period after exercise. During the post-exercise period plasma glucagon concentrations decreased but remained above pre-exercise values in rats treated with normal serum, while rats treated with antiglucagon serum has excess antibody in plasma throughout. Nevertheless, all other parameters measured showed similar changes in the two groups. Thus after exercise the grossly diminished hepatic glycogen concentrations remained constant, while the decreased blood glucose concentrations were partially restored. Simultaneously concentrations in blood and serum of the main gluconeogenic substrates, lactate, pyruvate, alanine and glycerol declined markedly. During the post-exercise period NEFA concentrations in serum and plasma insulin concentrations remained increased and decreased, respectively, while plasma catecholamines did not differ from basal values. Muscle glycogen concentration decreased slightly. These findings suggest that in the recovery period after exhausiive exercise the increased glucagon glucagon concentrations in plasma do not influence gluconeogenesis.

[Hypoglycaemic coma in Boeck's sarcoidosis (author's transl)]

The diversity of clinical manifestations of Boeck's sarcoidosis may also include endocrine disorders. One year after diagnosis of sarcoidosis in a 29 year-old female patient, endocrinological complications became manifest with amenorrhoea. The course of the disease was additionally complicated by hypoglycaemic episodes. Thorough clinical investigation of the patient revealed sarcoid involvement of the skin, lungs, liver and lymph nodes and an extensive retroperitoneal surgically-verified lymph tumour. After tolbutamide and in reaction to an intravenous glucose tolerance test the blood glucose was found to be very low, whilst the immunoreactive insulin was normal. Further investigation of the endocrine functions of the patient revealed normal functioning of the thyroid gland, subnormal values for the follicle stimulating hormone and extremely low serum ACTH and serum cortisol values, without any diurnal changes in these parameters. The clinical symptoms of the patient and the biochemical findings were regarded as manifestations of secondary adrenal failure due to sarcoid involvement of the hypothalamus and pituitary. Hence, treatment with corticosteroids was started. Hypoglycaemia has not since been observed in this patient and the other clinical features of (secondary) adrenal failure have disappeared slowly.

Effect of ethionine on carbohydrate and lipid metabolism

In ethionine-treated rats, the ATP content of adipose tissue was not decreased whereas in liver it was drastically reduced to about one-fifth of the control level. Shortly after the injection of ethionine, hepatic glycogen was depleted and the blood glucose concentration fell from 120 to 80 mg/100 ml. This was followed by a two- to threefold elevation of the plasma fatty acid level. Hepatic glucose-6-phosphate was decreased and was not elevated by administration of 2 mmoles of glucose unless ATP was partially restored to normal levels. When hepatic ATP was decreased, the disappearance of [(14)C]glucose from the blood and its incorporation into glycogen and glyceride-glycerol and the incorporation of [3-(14)C]pyruvate into glyceride-glycerol were reduced. 6 hr after ethionine injection the plasma triglyceride level fell but there was no significant change in the liver triglyceride concentration, but by 24 hr it had increased markedly. Lipogenesis in adipose tissue was depressed in vivo, possibly due to decreased glycerol-3-phosphate concentrations. A marked decrease of glycerol-3-phosphate in both liver and adipose tissue was noted. Administration of glucose effectively depressed plasma free fatty acid concentration and elevated the glycerol-3-phosphate levels. Ethionine injection to fasted animals further depressed the blood glucose and elevated the plasma free fatty acid level.

Dextrans and glycogens as particulate tracers for studying capillary permeability

Commercially available glycogens and dextrans can be used as biological particulate tracers in work on capillary permeability. These polysaccharides are well tolerated in intravenous injection and induce no vascular leakage when applied topically (cremaster test) in mice and in Wistar-Furth rats. The particles stain adequately with lead after aldehyde-OsO(4) fixation in phosphate buffer and provide a relatively wide set of probes ( approximately 45 A-300 A) for work on the large and small pore systems.