Glutamine administration promotes hepatic glucose homeostasis through regulating the PI3K/Akt pathway in high-fat diet-induced obese mice with limb ischemia.

High-fat diet-induced obesity can lead to hepatic insulin resistance (IR) and alter glucose metabolism. The decreased protein expression involved in the PI3K-Akt pathway may enhance hepatic glycogenolysis and gluconeogenesis. Obesity-associated glucose dysregulation and IR are risk factors for the development of peripheral arterial disease. Glutamine (Gln) has immunomodulatory properties and was found to attenuate IR and hyperglycemia in diabetic condition. Thus, in this study we hypothesized that Gln administration modulates hepatic glucose metabolism and improve IR via PI3K-Akt pathway in obese mice with limb ischemia. Mice were divided into a high-fat group (HC), and a high-fat Gln group (HG). Mice in the HC group were fed the high-fat diet for 8 weeks, while the HG group was initially fed the high-fat diet for 4 weeks followed by a high-fat diet with Gln for an additional 4 weeks. Part of the mice in the HC and HG groups were subjected to a limb ischemic operation and were euthanized after the operation. Liver tissues and blood samples were collected for analysis. The results showed that high-fat diet-induced obesity resulted in increased plasma glucose and insulin levels. Also, impairment of hepatic insulin signaling by downregulating PI3K-Akt pathway-associated protein expression was observed. Administration of Gln increased protein expression associated with PI3K-Akt signaling pathway, while reducing G6PC and FOXO1 expression in the hepatocytes that may promote glycogen synthesis and inhibit gluconeogenesis. These findings suggest that obese mice treated with Gln-containing high-fat diet may normalize blood glucose and improve IR in response to limb ischemia.

Hypoglycemic effect of deoxynojirimycin-polysaccharide on high fat diet and streptozotocin-induced diabetic mice via regulation of hepatic glucose metabolism.

Type 2 diabetes mellitus (T2DM) is currently considered a worldwide epidemic and finding effective therapeutic strategies against this disease is highly important. A deoxynojirimycin-polysaccharide mixture (DPM) has previously been shown to exert hypoglycemic effects on alloxan- or streptozotocin (STZ)-induced diabetic mice. The purpose of the present study was to evaluate the therapeutic effects and underlying mechanism(s) of DPM on T2DM induced by high fat diet following low-dose STZ treatment in mice. After daily oral treatment of diabetic mice with DPM (150 mg/kg b.w.) for 90 d, significant decline in blood glucose, pyruvate, triglyceride (TG), aspartate transaminase (AST), alanine transaminase (ALT), creatinine (Cr), lipid peroxide (LPO) and malondialdehyde (MDA) levels as well as evident increases in high density lipoprotein (HDL-c) and hepatic glycogen concentrations were observed. In the first stage, in which DPM was administered for 60 d, blood insulin levels did not undergo significant change but a significant decrease in the HOMA-IR index was detected. By contrast, the HOMA-IR index increased significantly in T2MD controls. In the second stage, in which DPM treatment was continued for another 30 d, insulin levels significantly increased in DPM-treated mice in comparison with T2DM controls. These results indicate that insulin resistance in the pre-diabetic period and the dysfunction of pancreatic ß-cells are ameliorated by DPM treatment. DPM also down-regulated protein levels of insulin receptor (IR) and gluconeogenic enzymes (pyruvate carboxylase, fructose-1, 6-bisphosphatase, phosphoenolpyruvate carboxykinase and glucose-6-phosphatase) in peripheral tissues (liver and/or muscle), but enhanced the expressions of insulin in pancreas, lipoprotein lipase (LPL) and glycolysis enzymes (glucokinase, phosphofructokinase, private kinase and pyruvate decarboxylase E1) in the liver. Furthermore, deoxynojirimycin (DNJ) and polysaccharide (P) were found to increase proliferation of hepatic LO-2 cells and scavenging of radicals in vitro. These results support the results of our biochemical analyses and underscore possible mechanisms underlying the protective effects of DPM on STZ-induced damage to the pancreas and the liver. Taken together, our findings suggest that DPM may be developed as an antihyperglycemic agent for the treatment of diabetes mellitus.

Profile of select hepatic insulin signaling pathway genes in response to 2-aminoanthracene dietary ingestion.

Some genes that regulate various processes such as insulin signaling, glucose metabolism, fatty acid, and lipid biosynthesis were profiled. The objective of the current investigation is to examine the mRNA expression of some genes that mediate insulin signaling due to 2AA toxicity. 2AA is a polycyclic aromatic hydrocarbon (PAH) that has been detected in broiled food and tobacco smoke. Twenty-four post-weaning 3-4-week-old F344 male rats were exposed to 0 mg/kg-diet, 50 mg/kg-diet, 75 mg/kg-diet, and 100 mg/kgdiet 2AA for 2 weeks and 4 weeks. The mRNA expression of AKT1, G6PC, GCK, GLUT4, INSR, IRS1, PP1R3C, PAMPK, SOCS 2, and SREBF1 was determined by qRTPCR followed by the quantification of G6PC and AMPK via ELISA. The results suggest that 2AA modulates these genes depending on the length of exposure. Up-regulation of AMPK and SOCS2 genes in animals treated with 100 mg/kg-diet and 50 mg/kg-diet, respectively, during 14 days of feeding was noted. G6PC expression was inhibited in the 2-week group while being dose-dependently increased in the 4-week group. Hepatic activity of G6PC was enhanced significantly in the livers of rats that ingested 2AA. It appears that 2AA intoxication leads to the activation of irs1 and akt1 genes in the liver. Quantified AMPK amounts increased significantly in the short-term treatment group. Dose-dependent rise of AMPK in animals treated to 2AA showed an increased production of hepatic AMPK in response to the toxicity of 2AA in order to maintain cellular homeostasis. In contrast, the reduction in AMPK concentration in treated animals within the 4-week set indicated an adaptive recovery.

Local autoantigen expression as essential gatekeeper of memory T-cell recruitment to islet grafts in diabetic hosts.

It is generally believed that inflammatory cues can attract noncognate, "bystander" T-cell specificities to sites of inflammation. We have shown that recruitment of naive and in vitro activated autoreactive CD8⁺ T cells into endogenous islets requires local autoantigen expression. Here, we demonstrate that absence of an autoantigen in syngeneic extrapancreatic islet grafts in diabetic hosts renders the grafts "invisible" to cognate memory (and naive) T cells. We monitored the recruitment of islet-specific glucose-6-phosphatase catalytic subunit-related protein (IGRP)206₋214-reactive CD8⁺ T cells into IGRP206₋214-competent and IGRP206₋214-deficient islet grafts in diabetic wild-type or IGRP206₋214(-/-) nonobese diabetic hosts (harboring either naive and memory T cells or only naive IGRP206₋214-specific T-cells, respectively). All four host-donor combinations had development of recurrent diabetes within 2 weeks. Wild-type hosts recruited IGRP206₋214-specific T cells into IGRP206₋214(+/+) but not IGRP206₋214(-/-) grafts. In IGRP206₋214(-/-) hosts, there was no recruitment of IGRP206₋214-specific T cells, regardless of donor type. Graft-derived IGRP206₋214 activated naive IGRP206₋214-specific T cells, but graft destruction invariably predated their recruitment. These results indicate that recurrent diabetes is exclusively driven by autoreactive T cells primed during the primary autoimmune response, and demonstrate that local antigen expression is a sine qua non requirement for accumulation of memory T cells into islet grafts. These findings underscore the importance of tackling autoreactive T-cell memory after ß-cell replacement therapy.

Histochemical demonstration of five enzymes' activities in Macrogyrodactylus clarii (Monogenea: Gyrodactylidae) from the catfish Clarias gariepinus.

Histochemical techniques were applied to whole mounts, to study the distribution of the enzymes alkaline phosphatase, acid phosphatase, adenosine triphosphatase, 5'-nucleotidase and glucose-6-phosphatase in the organs and tissues of a viviparous monogenean, Macrogyrodactylus clarii Gussev, 1961, from the gills of the North African catfish Clarias gariepinus (Burchell) in Egypt. The following organs and tissues were studied: head region, anterior adhesive glands, mouth region, pharynx, intestine, testis, vesicula seminalis, male accessory gland, male accessory reservoir, copulatory organ, receptaculum seminis, egg-cell forming region, embryonic cells, excretory system, nerve cells, haptor, muscle fibres and subtegumental cell bodies (cytons). The enzymes showed marked differences in their activities among the studied organs and tissues. Alkaline phosphatase and acid phosphatase activities were detected in many organs and tissues, while the activities of adenosine triphosphatase, 5'-nucleotidase and glucose-6-phosphatase were restricted to a few organs. Although no positive reaction for any enzyme was observed in the anterior adhesive gland cells, a positive reaction for acid phosphatase was detected in the anterior adhesive areas. All enzymes showed marked activity in the digestive and excretory systems. The distribution of the enzymes in the tissues and organs of M clarii is compared with those of other monogeneans, including other gyrodactylids parasitizing the same host fish. Some possible functions of the enzymes are discussed.

Ectopic expression of glucagon receptor in skeletal muscles improves glucose homeostasis in a mouse model of diabetes.

AIMS/HYPOTHESIS: Excessive secretion of glucagon partially contributes to the development of diabetic hyperglycaemia. However, complete blocking of glucagon action will lead to adverse effects, since glucagon exerts certain beneficial effects via its receptor in many organs. We aimed to study the effects of a 'decoy receptor' for circulating glucagon on modulating beta cell function and glucose homeostasis in mice by over-producing the glucagon receptor (GCGR) in skeletal muscles. METHODS: We generated transgenic mice in which the expression of Gcgr is driven by the muscle specific creatine kinase (Mck) promoter, and assessed the effects of glucagon on the modulation of glucose homeostasis under conditions of extremes of glucose influx or efflux. RESULTS: Mck/Gcgr mice showed increased circulating levels of glucagon and insulin, resulting in an unchanged ratio of glucagon-to-insulin. The levels of hepatic glucose-6-phosphatase (G6PC) and fructose-1,6-bisphosphatase (F1,6P2ase) were significantly decreased, whereas the phosphorylation level of pancreatic cAMP-response-element-binding-protein (CREB) was significantly increased in these transgenic mice. Under basal conditions, the mice displayed normal blood glucose levels and unchanged glucose tolerance and insulin sensitivity when compared with their age-matched wild-type (WT) littermates. However, following multiple low-dose streptozotocin injections, Mck/Gcgr mice exhibited a delay in the onset of hyperglycaemia compared with the WT controls. This was associated with preserved beta cell mass and beta cell secretory capacity in response to glucose challenge. CONCLUSIONS/INTERPRETATION: We suggest that mild and chronic hyperglucagonaemia, through a strategy involving neutralising peripheral glucagon action, provides beneficial effects on beta cell function and glucose homeostasis. Mck/Gcgr mice thus represent a novel mouse model for studying the physiological effects of glucagon.

Melatonin supplementation therapy as a potent alternative to ERT in ovariectomized rats.

AIM: To evaluate the efficacy of melatonin supplementation therapy as an alternative to estrogen replacement therapy in an ovariectomized rat model and to assess diabetogenic metabolic dysregulation caused by estrogen deficiency in postmenopausal individuals. METHODS: Ovariectomized adult Wistar rats were treated with either estrogen/progesterone, melatonin or a combination of estrogen and melatonin. Body weight gain, feed efficiency, serum glucose, insulin, glucose tolerance and insulin response, serum and tissue lipids, tissue glycogen contents and activities of glycogen phosphorylase and glucose-6-phosphatase were analyzed in all the experimental groups. RESULTS: Ovariectomized animals showed increased body weight gain, feed efficiency, fasting insulin resistance, greater area under curve for the glucose tolerance test, higher serum and tissue lipids and reduced glycogen content and insulin sensitivity. A low dose of melatonin was more efficient than estrogen in reversing all the ovariectomy-induced changes. The combination of estrogen + melatonin was found to be best in correcting glycemic dysregulation while high doses of melatonin could effectively regulate dyslipidemia. CONCLUSION: The present study provides strong evidence for melatonin supplementation therapy to be more potent and effective in comparison to estrogen replacement therapy due to its single-handed ability to revert all the ovariectomy-induced changes. No reported side-effect or long-term effect of melatonin, against the known effects of estrogen replacement therapy, make it more attractive as a candidate to treat postmenopausal symptoms.

Antidiabetic activity of alcoholic stem extract of Gymnema montanum in streptozotocin-induced diabetic rats.

In the present study, the effect of alcoholic stem extract of Gymnema montanum (GMSt) on blood glucose, plasma insulin, and carbohydrate metabolic enzymes were studied in experimental diabetes. Diabetes mellitus was induced by a single intraperitoneal injection of STZ (60 mg/kg bw). Five days after STZ induction, diabetic rats received GMSt orally at the doses of 25, 50, 100 and 200mg/kg daily for 3 weeks. Graded doses of stem extract showed a significant reduction in blood glucose levels and improvement in plasma insulin levels. The effect was more pronounced in 100 and 200mg/kg than 50mg/kg. GMSt showed significant increase in hexokinase, Glucose-6-phosphate dehydrogenase and glycogen content in liver of diabetic rats while there was significant reduction in the levels of glucose-6-phosphatase and fructose-1,6-bisphosphatase. The present study clearly indicated significant antidiabetic effect with the stem extract of G. montanum and lends support for its traditional usage.

Glucose transporters and enzymes related to glucose synthesis in small intestinal mucosa of mid-lactation dairy cows fed 2 levels of starch.

Diets containing corn starch may improve glucose supply by providing significant amounts of intestinal starch and increasing intestinal glucose absorption in dairy cows. Glucose absorption in the small intestine requires specific glucose transporters; that is, sodium-dependent glucose co-transporter-1 (SGLT1) and facilitated glucose transporter (GLUT2), which are usually downregulated in the small intestine of functional ruminants but are upregulated when luminal glucose is available. We tested the hypothesis that mRNA and protein expression of intestinal glucose transporters and mRNA expression of enzymes related to gluconeogenesis are affected by variable starch supply. Dairy cows (n=9/group) were fed for 4 wk total mixed rations (TMR) containing either high (HS) or low (LS) starch levels in the diet. Feed intake and milk yield were measured daily. After slaughter, tissue samples of the small intestinal mucosa (mid-duodenum and mid-jejunum) were taken for determination of mRNA concentrations of SGLT1 and GLUT2 as well as pyruvate carboxylase, cytosolic phosphoenolpyruvate carboxykinase, and glucose-6-phosphatase by real-time reverse transcription PCR relative to a housekeeping gene. Protein expression of GLUT2 in crude mucosal membranes and of SGLT1 and GLUT2 in brush-border membrane vesicles was quantified by sodium dodecyl sulfate-PAGE and immunoblot. A mixed model was used to examine feeding and time-related changes on feed intake and milk yield and to test feeding and gut site effects on gene or protein expression of glucose transporters and enzymes in the intestinal mucosa. Dry matter intake, but not energy intake, was higher in cows fed HS compared with LS. Abundance of SGLT1 mRNA tended to be higher in duodenal than in jejunal mucosa, and mRNA abundances of pyruvate carboxylase tended to be higher in jejunal than in duodenal mucosa. In brush-border membrane vesicles, SGLT1 and GLUT2 protein expression could be demonstrated. No diet-dependent differences were found concerning mRNA and protein contents of glucose transporter or mRNA level of gluconeogenic enzymes. In conclusion, our investigations on glucose transporters and gluconeogenic enzymes in the small intestinal mucosa of dairy cows did not show significant diet regulation when TMR with different amounts of intestinal starch were fed. Therefore, predicted intestinal glucose absorption after enhanced starch feeding is probably not supported by changes of intestinal glucose transporters in dairy cows.

Homogénéité mutationnelle de la glycogénose de type Ia en Tunisie.

The glycogen storage disease type Ia (GSD Ia) is a rare inherited disorder, with autosomal recessive determinism. It is characterized by hepatomegaly, short stature and hypoglycemia with lactic acidemia. The confirmation of diagnosis is based on the enzymatic assay performed on liver biopsy. For Tunisians patients, this biochemical test is performed abroad. The aim of our study is the molecular characterization of GSD Ia in Tunisian patients and the development of a molecular diagnosis tool. Our study included 27 patients from 23 unrelated families, mutation analysis revealed that the R83C mutation is the most frequent (65%, 30/46 mutant alleles), followed by the R170Q mutation (30%, 14/46 mutant alleles). The homogeneity of mutation spectrum of GSD Ia in Tunisia allows the development of a cost effective and reliable tool for the confirmation of clinical diagnosis among suspected GSD Ia patients.

Beneficiary effect of Tinospora cordifolia against high-fructose diet induced abnormalities in carbohydrate and lipid metabolism in Wistar rats.

High intake of dietary fructose has been shown to exert a number of adverse metabolic eff ects in humans and experimental animals. The present study was designed to investigate the eff ect of the aqueous extract of Tinospora cordifolia stem (TCAE) on the adverse eff ects of fructose loading toward carbohydrate and lipid metabolism in rats. Adult male Wistar rats of body weight around 200 g were divided into four groups, two of which were fed with starch diet and the other two with high fructose (66 %) diet. Plant extract of TC (400 mg/kg/day) was administered orally to each group of the starch fed rats and the highfructose fed rats. At the end of 60 days of experimental period, biochemical parameters related to carbohydrate and lipid metabolism were assayed. Hyperglycemia, hyperinsulinemia, hypertriglyceridemia, insulin resistance, and elevated levels of hepatic total lipids, cholesterol, triglycerides, and free fatty acids (p < 0.05) observed in fructose-fed rats were completely prevented with TCAE treatment. Alterations in the activities of enzymes of glucose metabolism (hexokinase, phosphofructokinase, pyruvate kinase, glucose-6-phosphatase, fructose-1,6-bisphosphatase, and glucose-6-phosphate dehydrogenase) and lipid metabolism (fatty acid synthetase, lipoprotein lipase, and malic enzyme) as observed in the high fructose-fed rats were prevented with TCAE administration. In conclusion, our fi ndings indicate improvement of glucose and lipid metabolism in high-fructose fed rats by treatment with Tinospora cordifolia, and suggest that the plant can be used as an adjuvant for the prevention and/or management of insulin resistance and disorders related to it.

Inhibition of hepatic glucose 6-phosphatase system by the green tea flavanol epigallocatechin gallate.

Effect of 5-100 microM epigallocatechin gallate (EGCG) on hepatic glucose 6-phosphatase (G6Pase) system was investigated. EGCG inhibited G6Pase in intact but not in permeabilized rat liver microsomes, suggesting the interference with the transport. However, EGCG did not hinder microsomal glucose 6-phosphate (G6P) uptake. Instead, it increased the accumulation of radioactivity after the addition of [(14)C]G6P, presumably due to a slower release of [(14)C]glucose, the product of luminal hydrolysis. Indeed, EGCG was found to inhibit microsomal glucose efflux. Since G6Pase activity is depressed by glucose in a concentration-dependent manner, we concluded that EGCG inhibits G6Pase through an elevated luminal glucose level.

Genetic variation in hepatic glucose-6-phosphatase system genes in cases of sudden infant death syndrome.

Genetic deficiencies of the hepatic glucose-6-phosphatase system, either of the enzyme (G6PC1) or of the glucose-6-phosphate transporter (G6PT1), result in fasting hypoglycaemia. Low hepatic G6PC1 activities were previously reported in a few term sudden infant death syndrome (SIDS) infants and assumed to be due to G6PC1 genetic deficiencies. In preterm infants, failures of postnatal activation of G6PC1 expression suggest disordered development as a novel cause of decreased G6PC1 activity in SIDS. G6PC1 and G6PT1 functional and mutational analysis was investigated in SIDS and non-SIDS infants. G6PC1 hepatic activity was abnormally low in 98 SIDS (preterm, n=13; term, n=85), and non-SIDS preterm infants (n=35) compared to term non-SIDS infants (n=29) and adults (n=9). Mean glycogen levels were elevated, except in term non-SIDS infants. A novel G6PT1 promoter polymorphism, 259C --> T was found; the - 259*T allele frequency was greater in term SIDS infants (n=140) than in term control infants (n=119) and preterm SIDS infants (n=30). Heterozygous and homozygous prevalence of 259C --> T was 38.6% and 7.1%, respectively, in term SIDS infants. In cell-based expression systems, the presence of - 259T in the promoter decreased basal luciferase activity by 3.2-fold compared to - 259C. Glucose-6-phosphatase latency in hepatic microsomes was elevated (indicating decreased G6PT1 function) in heterozygous and homozygous - 259T states. Delayed postnatal appearance of hepatic glucose-6-phosphatase in infants makes them vulnerable to hypoglycaemic episodes and this may occur in some SIDS infants. However, SIDS may be an association of more complex phenotypes in which several genes interact with multiple environmental factors. A UK-wide DNA Biobank of samples from all infant deaths, with an accompanying epidemiological database, should be established by pathologists to allow cumulative data to be collected from multiple genetic investigations on the same large cohort of samples, with the aim of selection of the best combination of genetic markers to predict unexpected infant death.

Impaired neutrophil activity and increased susceptibility to bacterial infection in mice lacking glucose-6-phosphatase-beta.

Neutropenia and neutrophil dysfunction are common in many diseases, although their etiology is often unclear. Previous views held that there was a single ER enzyme, glucose-6-phosphatase-alpha (G6Pase-alpha), whose activity--limited to the liver, kidney, and intestine--was solely responsible for the final stages of gluconeogenesis and glycogenolysis, in which glucose-6-phosphate (G6P) is hydrolyzed to glucose for release to the blood. Recently, we characterized a second G6Pase activity, that of G6Pase-beta (also known as G6PC), which is also capable of hydrolyzing G6P to glucose but is ubiquitously expressed and not implicated in interprandial blood glucose homeostasis. We now report that the absence of G6Pase-beta led to neutropenia; defects in neutrophil respiratory burst, chemotaxis, and calcium flux; and increased susceptibility to bacterial infection. Consistent with this, G6Pase-beta-deficient (G6pc3-/-) mice with experimental peritonitis exhibited increased expression of the glucose-regulated proteins upregulated during ER stress in their neutrophils and bone marrow, and the G6pc3-/- neutrophils exhibited an enhanced rate of apoptosis. Our results define a molecular pathway to neutropenia and neutrophil dysfunction of previously unknown etiology, providing a potential model for the treatment of these conditions.

Anti-diabetic effects of Cichorium intybus in streptozotocin-induced diabetic rats.

The present study was designed to investigate the hypoglycemic and hypolipidemic properties of an ethanolic extract of Cichorium intybus (CIE) which is widely used in India as a traditional treatment for diabetes mellitus. Male Sprague-Dawley rats aged 9 weeks (160-200 g) were administered with streptozotocin (STZ, 50mg/kg) intraperitoneally to induce experimental diabetes. The Cichorium intybus whole plant was exhaustively extracted with 80% ethanol, concentrated at 40 degrees C using a rotavapor and freeze dried to get powder. Hypoglycemic effects of CIE were observed in an oral glucose tolerance test (OGTT) in which, a dose of 125 mg of plant extract/kg body weight exhibited the most potent hypoglycemic effect. Moreover, daily administration of CIE (125 mg/kg) for 14 days to diabetic rats attenuated serum glucose by 20%, triglycerides by 91% and total cholesterol by 16%. However, there was no change in serum insulin levels, which ruled out the possibility that CIE induces insulin secretion from pancreatic beta-cells. In addition, hepatic glucose-6-phosphatase activity (Glc-6-Pase) was markedly reduced by CIE when compared to the control group. The reduction in the hepatic Glc-6-Pase activity could decrease hepatic glucose production, which in turn results in lower concentration of blood glucose in CIE-treated diabetic rats. In conclusion, our results support the traditional belief that Cichorium intybus could ameliorate diabetic state.

Effects of dexamethasone on the glucogenic capacity of fetal, pregnant, and non-pregnant adult sheep.

Fetal glucocorticoids have an important role in the pre-partum maturation of physiological systems essential for neonatal survival such as glucogenesis. Consequently, in clinical practice, synthetic glucocorticoids, like dexamethasone, are given routinely to pregnant women threatened with pre-term delivery to improve the viability of their infants. However, little is known about the effects of maternal dexamethasone treatment on the glucogenic capacity of either the fetus or mother. This study investigated the effects of dexamethasone treatment using a clinically relevant dose and regime on glycogen deposition and the activities of glucose-6-phosphatase (G6Pase) and phosphoenolpyruvate carboxykinase (PEPCK) in the liver and kidney of pregnant ewes and their fetuses, and of non-pregnant ewes. Dexamethasone administration increased the glycogen content of both the fetal and adult liver within 36 h of beginning treatment. It also increased G6Pase activity in the liver and kidney of the fetuses but not of their mothers or the non-pregnant ewes. Neither hepatic nor renal PEPCK activity was affected by dexamethasone in any group of animals. These changes in glycogen content and G6Pase activity were accompanied by rises in the plasma glucose and insulin concentrations and by a fall in the plasma cortisol level in the fetus and both groups of adult animals. In addition, dexamethasone treatment raised fetal plasma tri-iodothyronine (T(3)) concentrations and reduced maternal levels of plasma T(3) and thyroxine, but had no effect on thyroid hormone concentrations in the non-pregnant ewes. These findings show that maternal dexamethasone treatment increases the glucogenic capacity of both the mother and fetus and has major implications for glucose availability both before and after birth.

Dietary phenolic antioxidants, caffeic acid and Trolox, protect rainbow trout gill cells from nitric oxide-induced apoptosis.

Caffeic acid (CA) and Trolox are phenolic acids that have beneficial antioxidant effect, but the underlying mechanisms involved are not fully understood. The extent to which CA and Trolox protect against sodium nitroprusside (SNP)-induced oxidative cell injury was investigated in cultured rainbow trout gill cells. The cells exposed to SNP for 24 h displayed a dose-dependent leakage of lactate dehydrogenase (LDH) and decreased cell viability as indicated by the MTT assay (mitochondrial dehydrogenase activity). Both effects were prevented by treatment with 50 microM CA or Trolox. CA or Trolox, protected against SNP-induced caspase-3 activation and DNA fragmentation, indicating a reduction of apoptosis. Thus, the results indicate that SNP induced cell death is caspase-3 related apoptosis and the treatment with CA inhibited the apoptotic pathway. In addition, we studied the effect of CA and Trolox on expression of zinc-responsive antioxidant genes such as metallothioneins (MT), glutathione-S-transferase (GST Class pi) and glucose-6-phosphate dehydrogenase (G6PD) in cultured gill cells. CA, 100 microM, increased accumulation of mRNA for MTA, MTB, GST and G6PD in cells. Thus, in addition to its ability to sequester free radicals, CA may protect against oxidative stress through expression of zinc-induced antioxidant proteins. Because of these properties we suggest that CA could be a beneficial additive to fish feeds in aquaculture.

Early, sustained efficacy of adeno-associated virus vector-mediated gene therapy in glycogen storage disease type Ia.

The deficiency of glucose-6-phosphatase (G6Pase) underlies life-threatening hypoglycemia and growth retardation in glycogen storage disease type Ia (GSD-Ia). An adeno-associated virus (AAV) vector encoding G6Pase was pseudotyped as AAV8 and administered to 2-week-old GSD-Ia mice (n = 9). Median survival was prolonged to 7 months following vector administration, in contrast to untreated GSD-Ia mice that survived for only 2 weeks. Although GSD-Ia mice were initially growth-retarded, treated mice increased fourfold in weight to normal size. Blood glucose was partially corrected by 2 weeks following treatment, whereas blood cholesterol normalized. Glucose-6-phosphatase activity was partially corrected to 25% of the normal level at 7 months of age in treated mice, and blood glucose during fasting remained lower in treated, affected mice than in normal mice. Glycogen storage was partially corrected in the liver by 2 weeks following treatment, but reaccumulated to pre-treatment levels by 7 months old (m.o.). Vector genome DNA decreased between 3 days and 3 weeks in the liver following vector administration, mainly through the loss of single-stranded genomes; however, double-stranded vector genomes were more stable. Although CD8+ lymphocytic infiltrates were present in the liver, partial biochemical correction was sustained at 7 m.o. The development of efficacious AAV vector-mediated gene therapy could significantly reduce the impact of long-term complications in GSD-Ia, including hypoglycemia, hyperlipidemia and growth failure.

Rutin improves glucose homeostasis in streptozotocin diabetic tissues by altering glycolytic and gluconeogenic enzymes.

The role of rutin on carbohydrate metabolism in normal and streptozotocin (STZ)-induced diabetic rats was investigated in the present study. Administration of STZ led to a significant (p <0.05) increase in fasting plasma glucose and a decrease in insulin levels. The content of glycogen significantly (p <0.05) decreased in liver and muscle, but increased in kidney. The activity of hexokinase decreased whereas the activities of glucose-6-phosphatase and fructose-1,6-bisphosphatase significantly (p <0.05) increased in the tissues. Oral administration of rutin (100 mg/kg) to diabetic rats for a period of 45 days resulted in significant (p <0.05) alterations in the parameters studied but not in normal rats. A decrease of plasma glucose and increase in insulin levels were observed along with the restoration of glycogen content and the activities of carbohydrate metabolic enzymes in rutin-treated diabetic rats. The histopathological study of the pancreas revealed the protective role of rutin. There was an expansion of the islets and decreased fatty infiltrate of the islets in rutin-treated diabetic rats. In normal rats treated with rutin, we could not observe any significant change in all the parameters studied. Combined, these results show that rutin plays a positive role in carbohydrate metabolism and antioxidant status in diabetic rats.

Effect of fasting on carbohydrate metabolism in frugivorous bats (Artibeus lituratus and Artibeus jamaicensis).

The compensatory changes of carbohydrate metabolism induced by fasting were investigated in frugivorous bats, Artibeus lituratus and Artibeus jamaicensis. For this purpose, plasma levels of glucose and lactate, liver and muscle glycogen content, rates of liver gluconeogenesis and the activity of related enzymes were determined in male bats. After a decrease during the first 48 h of fasting, plasma glucose levels remained constant until the end of the experimental period. Plasma lactate levels, extremely high in fed bats, decreased after 48 h of fasting. Similarly, liver glycogen content, markedly high in fed animals, was reduced to low levels after 24 h without food. Muscle glycogen was also reduced in fasted bats. The expected increase in liver gluconeogenesis during fasting was observed after 48 h of fasting. The activities of liver glucose-6-phosphatase and fructose-1,6-bisphosphatase were not affected by food withdrawn. On the other hand, fasting for 24 h induced an increase in the activity of liver cytosolic phosphoenolpyruvate carboxykinase. The data indicate that liver gluconeogenesis has an important role in the glucose homeostasis in frugivorous bats during prolonged periods of food deprivation. During short periods of fasting liver glycogenolysis seems to be the main responsible for the maintenance of glycemia.