Defect in degradation of glycogenin-exposed residual glycogen in lysosomes is the fundamental pathomechanism of Pompe disease.

Pompe disease is a lysosomal storage disorder that preferentially affects muscles, and it is caused by GAA mutation coding acid alpha-glucosidase in lysosome and glycophagy deficiency. While the initial pathology of Pompe disease is glycogen accumulation in lysosomes, the special role of the lysosomal pathway in glycogen degradation is not fully understood. Hence, we investigated the characteristics of accumulated glycogen and the mechanism underlying glycophagy disturbance in Pompe disease. Skeletal muscle specimens were obtained from the affected sites of patients and mouse models with Pompe disease. Histological analysis, immunoblot analysis, immunofluorescence assay, and lysosome isolation were utilized to analyze the characteristics of accumulated glycogen. Cell culture, lentiviral infection, and the CRISPR/Cas9 approach were utilized to investigate the regulation of glycophagy accumulation. We demonstrated residual glycogen, which was distinguishable from mature glycogen by exposed glycogenin and more α-amylase resistance, accumulated in the skeletal muscle of Pompe disease. Lysosome isolation revealed glycogen-free glycogenin in wild type mouse lysosomes and variously sized glycogenin in Gaa-/- mouse lysosomes. Our study identified that a defect in the degradation of glycogenin-exposed residual glycogen in lysosomes was the fundamental pathological mechanism of Pompe disease. Meanwhile, glycogenin-exposed residual glycogen was absent in other glycogen storage diseases caused by cytoplasmic glycogenolysis deficiencies. In vitro, the generation of residual glycogen resulted from cytoplasmic glycogenolysis. Notably, the inhibition of glycogen phosphorylase led to a reduction in glycogenin-exposed residual glycogen and glycophagy accumulations in cellular models of Pompe disease. Therefore, the lysosomal hydrolysis pathway played a crucial role in the degradation of residual glycogen into glycogenin, which took place in tandem with cytoplasmic glycogenolysis. These findings may offer a novel substrate reduction therapeutic strategy for Pompe disease. © 2024 The Pathological Society of Great Britain and Ireland.

Magnetic resonance imaging of glycogen using its magnetic coupling with water.

Glycogen plays a central role in glucose homeostasis and is abundant in several types of tissue. We report an MRI method for imaging glycogen noninvasively with enhanced detection sensitivity and high specificity, using the magnetic coupling between glycogen and water protons through the nuclear Overhauser enhancement (NOE). We show in vitro that the glycogen NOE (glycoNOE) signal is correlated linearly with glycogen concentration, while pH and temperature have little effect on its intensity. For validation, we imaged glycoNOE signal changes in mouse liver, both before and after fasting and during glucagon infusion. The glycoNOE signal was reduced by 88 ± 16% (n = 5) after 24 h of fasting and by 76 ± 22% (n = 5) at 1 h after intraperitoneal (i.p.) injection of glucagon, which is known to rapidly deplete hepatic glycogen. The ability to noninvasively image glycogen should allow assessment of diseases in which glucose metabolism or storage is altered, for instance, diabetes, cardiac disease, muscular disorders, cancer, and glycogen storage diseases.

Endometrial glycogen metabolism during early pregnancy in mice.

Glucose is critical during early pregnancy. The uterus can store glucose as glycogen but uterine glycogen metabolism is poorly understood. This study analyzed glycogen storage and localization of glycogen metabolizing enzymes from proestrus until implantation in the murine uterus. Quantification of diastase-labile periodic acid-Schiff (PAS) staining showed glycogen in the glandular epithelium decreased 71.4% at 1.5 days postcoitum (DPC) and 62.13% at DPC 3.5 compared to proestrus. In the luminal epithelium, glycogen was the highest at proestrus, decreased 46.2% at DPC 1.5 and 63.2% at DPC 3.5. Immunostaining showed that before implantation, glycogen metabolizing enzymes were primarily localized to the glandular and luminal epithelium. Stromal glycogen was low from proestrus to DPC 3.5. However, at the DPC 5.5 implantation sites, stromal glycogen levels increased sevenfold. Similarly, artificial decidualization resulted in a fivefold increase in glycogen levels. In both models, decidualization increased expression of glycogen synthase as determine by immunohistochemistry and western blot. In conclusion, glycogen levels decreased in the uterine epithelium before implantation, indicating that it could be used to support preimplantation embryos. Decidualization resulted in a dramatic increase in stromal glycogen levels, suggesting it may have an important, but yet undefined, role in pregnancy.

Sarcoplasmic and myofibrillar phosphoproteins profile of beef M. longissimus thoracis with different pHu at different days postmortem.

BACKGROUND: The abnormal ultimate pH (pHu ) in postmortem muscles affect the meat quality and results in substantial economic losses. Dark, firm, and dry (DFD) meat linked with the higher postmortem pHu values and exhibited many quality issues such as dark color, tough texture and shorter shelf life. This research aimed to investigate the effect of protein phosphorylation on variations in beef pHu in order to explore the possible mechanisms underlying DFD meat formation. RESULTS: Glycogen and lactate contents were higher, while L* and a* were lower in high pHu beef. Shear force was higher in intermediate pHu group. Global phosphorylation of sarcoplasmic proteins was higher in low pHu samples on day 1 and of myofibrillar proteins was higher in intermediate pHu meat on days 1 and 2 postmortem. Sarcoplasmic protein bands with different phosphorylation levels were identified as containing some glycometabolism and stress response proteins and phosphorylated myofibrillar protein bands were identified sarcomeric and metabolic proteins. CONCLUSIONS: Phosphorylation of multiple proteins of glycolytic pathway and contractile machinery may play critical roles in development of DFD beef. © 2021 Society of Chemical Industry.

Chemical exchange rotation transfer imaging of phosphocreatine in muscle.

In chemical exchange saturation transfer (CEST) imaging, the signal at 2.6 ppm from the water resonance in muscle has been assigned to phosphocreatine (PCr). However, this signal has limited specificity for PCr since the signal is also sensitive to exchange with protein and macromolecular protons when using some conventional quantification methods, and will vary with changes in the water longitudinal relaxation rate. Correcting for these effects while maintaining reasonable acquisition times is challenging. As an alternative approach to overcome these problems, here we evaluate chemical exchange rotation transfer (CERT) imaging of PCr in muscle at 9.4 T. Specifically, the CERT metric, AREXdouble,cpw at 2.6 ppm, was measured in solutions containing the main muscle metabolites, in tissue homogenates with controlled PCr content, and in vivo in rat leg muscles. PCr dominates CERT metrics around 2.6 ppm (although with nontrivial confounding baseline contributions), indicating that CERT is well-suited to PCr specific imaging, and has the added benefit of requiring a relatively small number of acquisitions.

Maternal choline supplementation in a rat model of periconceptional alcohol exposure: Impacts on the fetus and placenta.

BACKGROUND: Maternal choline supplementation in rats can ameliorate specific neurological and behavioral abnormalities caused by alcohol exposure during pregnancy. We tested whether choline supplementation ameliorates fetal growth restriction and molecular changes in the placenta associated with periconceptional ethanol exposure (PCE) in the rat. METHODS: Sprague Dawley dams were given either 12.5% ethanol (PCE) or 0% ethanol (Con) in a liquid diet from 4 days prior to 4 days after conception. At day 5 of pregnancy, dams were either placed on a standard chow (1.6 g choline/kg chow) or an intermediate chow (2.6 g choline/kg chow). On day 10 of pregnancy, a subset of the intermediate dams were placed on a chow further supplemented with choline (7.2 g choline/kg chow), resulting in 6 groups. Fetuses and placentas were collected on day 20 of pregnancy for analysis. RESULTS: Choline supplementation resulted in increased fetal weight at late gestation, ameliorating the deficits due to PCE. This was most pronounced in litters on a standard chow during pregnancy. Choline also increased fetal liver weight and decreased fetal brain:liver ratio, independent of alcohol exposure. Placental weight was reduced as choline levels in the chow increased, particularly in female placentas. This resulted in a greater ratio of fetal:placental weight, suggesting increased placental efficiency. Global DNA methylation in the placenta was altered in a sex-specific manner by both PCE and choline. However, the increased glycogen deposition in female placentas, previously reported in this PCE model, was not prevented by choline supplementation. CONCLUSIONS: Our results suggest that choline has the potential to ameliorate fetal growth restriction associated with PCE and improve placental efficiency following prenatal alcohol exposure. Our study highlights the importance of maternal nutrition in moderating the severity of adverse fetal and placental outcomes that may arise from prenatal alcohol exposure around the time of conception.

Sodium metavanadate treatment improves glycogen levels in multiple tissues in a model of metabolic syndrome caused by chronic cadmium exposure in Wistar rats.

Cadmium, one of the more hazardous environmental contaminants, has been proposed as a metabolic disruptor. Vanadium has emerged as a possible treatment for metabolic diseases. Both metals are important in public health. We aimed to investigate whether vanadium treatment is effective against metabolic disturbances caused by chronic exposure to the lowest-observable adverse effect level of cadmium. Male Wistar rats were exposed to cadmium (32.5 ppm) in drinking water for 3 months. Metabolic complications such as overweight, visceral adipose gain, hyperglycemia, impaired glucose tolerance, and dyslipidemia were detected, and low glycogen levels and steatosis were observed in the tissues. Then, the control and treated animals were subdivided and treated with a solution of 5 µM NaVO3/kg/twice a week for 2 months. The control-NaVO3 group did not show zoometric or metabolic changes. A strong interaction of NaVO3 treatment over cadmium metabolic disruption was observed. The vanadium accumulation diminished cadmium concentration in tissues. Also, vanadium interaction improved glucose homeostasis. The major effect was observed on glycogen synthesis, which was fully recovered in all tissues analyzed. Additionally, vanadium treatment prevented overweight and visceral fat accumulation, improving BMI and the percentage of fat. However, NaVO3 treatment did not have an effect on dyslipidemia or steatosis. In conclusion, this work shows that vanadium administration has a strong effect against metabolic disturbances caused by chronic cadmium exposure, observing powerful interaction on glucose homeostasis.

Variation of skeletal muscle ultrasound imaging intensity in horses after treadmill exercise: a proof of concept for glycogen content estimation.

BACKGROUND: Glycogen in skeletal muscle is a major source of energy during exercise and an important determinant of endurance capacity, so that its measurement may provide a meaningful marker of athletes' preparation and a possible predictor of performance, both in humans and in equines. Gold standard of glycogen concentration measurement is the histochemical and biochemical analysis of biopsy-derived muscle tissue, an invasive and potentially injuring procedure. Recently, high-frequency ultrasound (US) technology is being exploited in human sports medicine to estimate muscle glycogen content. Therefore, aim of the present study is to evaluate the feasibility of US assessment of muscle glycogen in equines. RESULTS: US images of gluteus medius (GL) and semitendinosus (ST) muscles were obtained on eight healthy horses (3-10 years) before and after a steady-state exercise on treadmill (velocity: 4.0-12.5 m/s; duration: 2-20 min; heart rate: 137-218 b/min). Average image greyscale intensity was significantly different between GL and ST, both before and after exercise (p < 0.001). Comparing baseline and post-exercise US images, significant increase in greyscale intensity has been observed in ST (p < 0.001), but not in GL (p = 0.129). The volume of the exercise was significantly correlated with exercise-dependent change in image intensity (R2 = 0.891), consistent with a reduction of glycogen muscle stores resulting from aerobic activity. CONCLUSIONS: US technique evidences also in horses muscle changes possibly associated to glycogen utilisation during exercise. Present results on a small sample need to be further confirmed and provide preliminary data warranting future validation by direct glycogen measurement through biopsy technique.

Structure and Immunomodulatory Activity of Glycogen Derived from Honeybee Larvae (Apis mellifera).

Honeybee larvae have been recognized as nutrient-rich food in many countries. Although glycogen, a storage form of glucose in animals, is synthesized in honeybee larvae, there is no information on the structure of glycan and its biological activity. In this study, we successfully extracted glycogen from honeybee larvae using hot water extraction and investigated the structure and biological activity of glycan. It was found that the molecular weight of glycogen from honeybee larvae is higher than that of glycogen from bovine liver and oysters. In addition, treatment of RAW264.7 cells with glycogen from honeybee larvae resulted in a much higher production of tumor necrosis factor (TNF)-α and interleukin (IL)-6 than treatment with glycogen from either bovine liver or oysters. These results suggest that the high molecular weight glycogen from honeybee larvae is a functional food ingredient with immunomodulatory activity.

The effects of exercise training versus intensive insulin treatment on skeletal muscle fibre content in type 1 diabetes mellitus rodents.

BACKGROUND: Intensive-insulin treatment (IIT) strategy for patients with type 1 diabetes mellitus (T1DM) has been associated with sedentary behaviour and the development of insulin resistance. Exercising patients with T1DM often utilize a conventional insulin treatment (CIT) strategy leading to increased insulin sensitivity through improved intramyocellular lipid (IMCL) content. It is unclear how these exercise-related metabolic adaptations in response to exercise training relate to individual fibre-type transitions, and whether these alterations are evident between different insulin strategies (CIT vs. IIT). PURPOSE: This study examined glycogen and fat content in skeletal muscle fibres of diabetic rats following exercise-training. METHODS: Male Sprague-Dawley rats were divided into four groups: Control-Sedentary, CIT- and IIT-treated diabetic sedentary, and CIT-exercised trained (aerobic/resistance; DARE). After 12 weeks, muscle-fibre lipids and glycogen were compared through immunohistochemical analysis. RESULTS: The primary findings were that both IIT and DARE led to significant increases in type I fibres when compared to CIT, while DARE led to significantly increased lipid content in type I fibres compared to IIT. CONCLUSIONS: These findings indicate that alterations in lipid content with insulin treatment and DARE are primarily evident in type I fibres, suggesting that muscle lipotoxicity in type 1 diabetes is muscle fibre-type dependant.

Visualizing Subcellular Enrichment of Glycogen in Live Cancer Cells by Stimulated Raman Scattering.

Glycogen, a branched glucose polymer, helps regulate glucose homeostasis through immediate storage and release of glucose. Reprogramming of glycogen metabolism has recently been suggested to play an emerging role in cancer progression and tumorigenesis. However, regulation of metabolic rewiring for glycogen synthesis and breakdown in cancer cells remains less understood. Despite the availability of various glycogen detection methods, selective visualization of glycogen in living cells with high spatial resolution has proven to be highly challenging. Here, we present an optical imaging strategy to visualize glycogen in live cancer cells with minimal perturbation by combining stimulated Raman scattering microscopy with metabolic incorporation of deuterium-labeled glucose. We revealed the subcellular enrichment of glycogen in live cancer cells and achieved specific glycogen mapping through distinct spectral identification. Using this method, different glycogen metabolic phenotypes were characterized in a series of patient-derived BRAF mutant melanoma cell lines. Our results indicate that cell lines manifesting high glycogen storage level showed increased tolerance to glucose deficiency among the studied melanoma phenotypes. This method opens up the possibility for noninvasive study of complex glycogen metabolism at subcellular resolution and may help reveal new features of glycogen regulation in cancer systems.

Single-Cell Analysis for Glycogen Localization and Metabolism in Cultured Astrocytes.

Cerebral glycogen is principally localized in astrocytes rather than in neurons. Glycogen metabolism has been implicated in higher brain functions, including learning and memory, yet the distribution patterns of glycogen in different types of astrocytes have not been fully described. Here, we applied a method based on the incorporation of 2-NBDG, a D-glucose fluorescent derivative that can trace glycogen, to investigate glycogen's distribution in the brain. We identified two types of astrocytes, namely, 2-NBDGI (glycogen-deficient) and 2-NBDGII (glycogen-rich) cells. Whole-cell patch-clamp and fluorescence-activated cell sorting (FACS) were used to separate 2-NBDGII astrocytes from 2-NBDGI astrocytes. The expression levels of glycogen metabolic enzymes were analyzed in 2-NBDGI and 2-NBDGII astrocytes. We found unique glycogen metabolic patterns between 2-NBDGI and 2-NBDGII astrocytes. We also observed that 2-NBDGII astrocytes were mainly identified as fibrous astrocytes but not protoplasmic astrocytes. Our data reveal cell type-dependent glycogen distribution and metabolism patterns, suggesting diverse functions of these different astrocytes.

Fluid Brain Glycolysis: Limits, Speed, Location, Moonlighting, and the Fates of Glycogen and Lactate.

Glycolysis is the core of intermediate metabolism, an ancient pathway discovered in the heydays of classic biochemistry. A hundred years later, it remains a matter of active research, clinical interest and is not devoid of controversy. This review examines topical aspects of glycolysis in the brain, a tissue characterized by an extreme dependence on glucose. The limits of glycolysis are reviewed in terms of flux control by glucose transporters, intercellular lactate shuttling and activity-dependent glycolysis in astrocytes and neurons. What is the site of glycogen mobilization and aerobic glycolysis in brain tissue? We scrutinize the pervasive notions that glycolysis is fast and that catalysis is channeled through supramolecular assemblies. In brain tissue, most glycolytic enzymes are catalytically silent. What then is their function?

Physiological activity of Aloe vera in pacu (Piaractus mesopotamicus) inoculated with Aeromonas hydrophila.

Aloe vera is a traditional medicinal plant; however, its use in fish is fairly recent. We evaluated the effects of dietary A. vera on stress, innate immunity, and energy metabolism in pacu inoculated with Aeromonas hydrophila. For 7 days, 192 fish were fed with diets supplemented with 0% (control), 0.5%, 1.0%, and 2.0% of the plant extract and then inoculated with bacteria and sampled 3, 6, and 24 h later. All concentrations of A. vera reduced basal levels of cortisol, and 1.0% reduced cortisol levels more intensely 3 h after inoculation. A. vera increased the basal respiratory activity of leukocytes/RAL (0.5 and 1.0%), increased the serum levels of lysozyme (1.0 and 2.0%) 6 h after inoculation, and increased the activity of the complement system after 3 h. Spleen somatic index/SSI increased with 1.0 and 2.0% A. vera. A. vera also promoted metabolic effects. It increased basal levels of lipids in the liver and muscle, as well as hepatosomatic index (1.0%) and, 3 h after inoculation, prevented the reduction of serum triglyceride (1.0%) and reduced the mesenteric fat (1.0%). Bacterial inoculation increased RAL from 3 to 24 h and lysozyme levels at 24 h, increased serum cholesterol at 24 h, and decreased serum triglyceride from 3 to 24 h, regardless of A. vera. We concluded that A. vera offered for only 7 days had stress-reducing effects, stimulated innate immunity, protected triglyceride levels in blood, lipid depots in the liver and muscle, and directed the energy mobilization to visceral depots.

Assessment of Rhodopirellula rubra as a supplementary and nutritional food source to the microcrustacean Daphnia magna.

The daily use of the planctomycete Rhodopirellula rubra as an alternative or supplementary food source for Daphnia magna and its feasibility in the nutrition of transgenerational populations were studied. The life history parameters, fatty acids (saturated, mono- and polyunsaturated; SFAs, MUFAs and PUFAs), glycogen and protein contents of organisms during feeding assays and of the first generation were analysed. An increase in the yields of D. magna with the increase of the cell concentration of R. rubra was evident, but overall, bacteria supplied as the only food source was nutritionally insufficient as observed for all the parameters analysed. However, when R. rubra was added as supplement to the microalgae Raphidocelis subcapitata a significant improvement in the life history parameters was observed namely in the reproductive output and the somatic growth rate. The identified SFAs, MUFAs and PUFAs were the fatty acids more abundant in daphniids, and the feed regimens influenced daphniids fatty acid profiles. Additionally, the mixed diet resulted in a larger number and size of offspring in the different F1 broods as also observed with the results of F0 generation. The pink colouration present in D. magna body and eggs confirmed that bacteria were absorbed, the pigment(s) retained and passed on to the next generation. Our results showed that R. rubra can play an essential role in D. magna diet as a nutritional supplement showing potential biotechnological applications.

First ultrastructural and cytochemical data on the spermatozoon and its differentiation in progenetic and adult Archigetes sieboldi Leuckart, 1878 (Cestoda, Caryophyllidea, Caryophyllaeidae).

Spermiogenesis in progenetic and adult stages of Archigetes sieboldi Leuckart, 1878, a tapeworm parasitic in oligochaetes and fish respectively, has been examined using transmission electron microscopy and cytochemical staining for glycogen. General pattern of spermiogenesis is essentially like that of other caryophyllideans, i.e., apical dense material in the zone of differentiation in the early stages of spermiogenesis, rotation of free flagellum and a flagellar bud, and proximo-distal fusion. Interestingly, rotation of a free flagellum and flagellar bud to the median cytoplasmic process (MCP) has been observed unconventionally at > 90° only in progenetic stages. Typical striated roots associated with the centrioles occur rarely in A. sieboldi, and only in form of faint structures in advanced stages of spermiogenesis. In contrast to most caryophyllideans studied to date, penetration of the nucleus into the spermatid body has started before the fusion of the free flagellum with the MCP. This feature has been reported rarely but exclusively in the family Caryophyllaeidae. The unipartite mature spermatozoon of A. sieboldi is composed of one axoneme of the 9 + '1' trepaxonematan pattern with its centriole, parallel nucleus, and parallel cortical microtubules which are situated in a moderately electron-dense cytoplasm with glycogen particles. An unusual arrangement of cortical microtubules in the two parallel rows in region I of the spermatozoon is described here for the first time in the Caryophyllidea. Ultrastructural data on spermiogenesis and the spermatozoon in A. sieboldi from tubuficids and carp are compared and discussed with those in other caryophyllideans and/or Neodermata.

Probiotic Lactobacillus gasseri SBT2055 improves insulin secretion in a diabetic rat model.

The probiotic Lactobacillus gasseri SBT2055 (LG2055) has a protective effect against metabolic syndrome in rats and humans. Metabolic syndrome increases the risk of type 2 diabetes mellitus. In this study, Goto-Kakizaki rats were used as a diabetic model and fed diets containing LG2055-fermented or nonfermented skim milk for 4 wk. Indices of diabetes such as blood glucose levels, serum glucagon levels, plasma levels of insulin, C-peptide, and glucagon-like peptide-1, tissue glycogen contents, and pancreatic mRNA levels were measured. The plasma C-peptide levels and pancreatic mRNA levels of insulin genes (Ins1 and Ins2) and Pdx1 (a transcriptional factor of insulin genes) were increased in LG2055 diet-fed rats. The increase in insulin secretion corresponded to an improvement in serum and pancreatic inflammatory status, associated with decreases in serum levels of serum amyloid P and pancreatic levels of granulocyte colony-stimulating factor. Insulin resistance in Goto-Kakizaki rats was ameliorated by increased glycogen storage in the liver and quadriceps femoris muscles and decreased serum free fatty acid levels. This improvement may be related to the increased cecal production of short-chain fatty acids. In conclusion, dietary LG2055 improved insulin secretion in diabetic rats by improving the inflammatory status in the pancreas and serum.

Variation in Glycogen Distribution among Freshwater Bivalve Tissues: Simplified Protocol and Implications.

Glycogen is a primary metabolic reserve in bivalves and can be suitable for the evaluation of bivalve condition and health status, but the use of glycogen as a diagnostic tool in aquaculture and biomonitoring is still relatively rare. A tissue biopsy combined with a simplified phenol-sulfuric acid method was used in this study to evaluate the inter- and intraindividual variation in the glycogen concentrations among several tissues (foot, mantle, gills, adductor muscle) of the unionid bivalve, the duck mussel Anodonta anatina. This short report documents that individual bivalves differ in the spatial distribution of glycogen among tissues. Sampling of different types of tissues can cause distinct results in the evaluation of energetic reserves at the individual level. At the same time, spatial variability in glycogen content has the potential to provide a more detailed evaluation of physiological conditions based on tissue-specific glycogen storage. The results obtained and the simplified methodology provide a new opportunity for researching the energetic reserves and health status of freshwater mussels in various applications.

Liver Plays a Major Role in FGF-21 Mediated Glucose Homeostasis.

BACKGROUND/AIMS: The liver is a vital organ in vertebrates and has a wide range of functions, including glucose absorption, glycogen storage and glucose production. Fibroblast growth factor (FGF)-21 is a metabolic regulator that is primarily produced by the liver. In this paper, we studied the effect of FGF-21 on glucose metabolism in the liver. METHODS: The glucose uptake of cells was detected by 2-Deoxy-d-[3H] glucose; the synergy between insulin and FGF-21 was evaluated. The mRNA expression of GLUT1-4, G6Pase and PEPCK was detected by real-time PCR. Glycogen synthesis was examined by the anthrone method. Blood samples to monitor glucose in db/db diabetic mice were obtained by tail snip. Glucose metabolism in the liver and adipose tissues was observed by fluorescence microscopy. RESULTS: In this study, FGF-21 stimulated glucose uptake by liver cells in both a dose and time-dependent manner, and at the same time, FGF-21 specifically stimulated GLUT1 expression in the liver cells. Furthermore, FGF-21 demonstrated a synergistic effect with insulin on glucose absorption, which is in accordance with enhanced GLUT-1 and -4 expression. Treatment with FGF-21 increased glycogen storage in liver cells. Consistent with in vitro results, FGF-21 lowered the plasma glucose level and stimulated GLUT1 expression and glycogen synthesis in db/db diabetic mice. Simultaneously, FGF-21 inhibited the gene expression of G6Pase and PEPCK. CONCLUSION: Our results suggest that FGF-21 clears up plasma glucose by stimulating glucose absorption in the liver of diabetic animals and decreases glucose release from the liver by inhibiting gluconeogenesis. Overall, these data indicate that the liver is an important target organ of FGF-21 to regulate glucose metabolism.

The Endocannabinoid System Affects Myocardial Glucose Metabolism in the DOCA-Salt Model of Hypertension.

BACKGROUND/AIMS: Recent interest in the use of cannabinoids as therapeutic agents has revealed the involvement of the endogenous cannabinoid system (ECS) in the regulation of the cardiovascular system in hypertension. Abnormalities in glucose metabolism and insulin action are commonly detected in hypertensive animals. Thus, potential antihypertensive drugs should be investigated with respect to modulation of glucose homeostasis. Therefore, the aim of the present study was to evaluate the effects of the ECS activation after chronic fatty acid amide hydrolase inhibitor (URB597) administration on plasma glucose and insulin concentrations as well as parameters of myocardial glucose metabolism in the deoxycorticosterone acetate (DOCA)-salt hypertensive rats, an animal model of secondary hypertension. METHODS: Hypertension was induced by DOCA (25mg/kg) injections and addition of 1% NaCl in the drinking water for six weeks. Chronic activation of the ECS was performed by URB597 (1mg/kg) injections for two weeks. We examined fasting plasma levels of insulin (ELISA), glucose and intramyocardial glycogen (colorimetric method). Expressions of glucose transporters (GLUT1, 4) and selected proteins engaged in GLUT translocation as well as glucose metabolism were determined using Western blotting. RESULTS: Hypertension induced hypoinsulinemia with concomitant lack of significant changes in glycemia, reduced intramyocardial glycogen content and increased pyruvate dehydrogenase (PDH) expression in the cardiac muscle. Importantly, chronic URB597 administration in the hypertensive rats increased insulin concentration, elevated plasmalemmal GLUT1 and GLUT4 expression and concomitantly improved myocardial glycogen storage. CONCLUSION: Chronic administration of fatty acid amide hydrolase (FAAH) inhibitor has potential protective properties on myocardial glucose metabolism in hypertension.