Glycogen Utilization Research Articles

Effects of Acute Aerobic Exercise on Skeletal Muscle and Liver Glucose Metabolism in Male Rodents with Type 1 Diabetes.

Aerobic exercise (AE) is associated with a significant hypoglycemia risk in individuals with type 1 diabetes mellitus (T1DM). However, the mechanisms in the liver and skeletal muscle governing exercise-induced hypoglycemia in T1DM are poorly understood. This study examined the effects of a 60-minute bout of AE on hepatic and muscle glucose metabolism in T1DM rats. Nineteen male Sprague-Dawley rats were divided into sedentary (SC; n=5) and T1DM (DSC; n=14) groups. T1DM rats were subcategorized into pre-exercise (DPRE; n=6) and post-exercise (DPOST; n=8). DPOST were sacrificed immediately after 60-minute of AE. Results demonstrate that DPOST animals experienced reductions in BG following 30 and 60 minutes of AE compared to pre-exercise. Both DPRE and DPOST animals exhibited lower hepatic glycogen content, while muscle glycogen did not differ, suggesting impaired glycogenolysis in T1DM. Hepatic glycogen-6-phosphatase content, and muscle and hepatic protein kinase B phosphorylation were significantly greater in DPOST animals, suggesting elevated gluconeogenesis and insulin stimulation during exercise. Glycogen phosphorylase activity did not differ between groups. These data suggest that drops in BG during AE in T1DM were due to lower glycogen levels in the liver and muscle and a lack of muscle glycogen utilization; leading to a reliance on gluconeogenesis and BG.

Does AMPK bind glycogen in skeletal muscle or is the relationship correlative?

Since its discovery over five decades ago, an emphasis on better understanding the structure and functional role of AMPK has been prevalent. In that time, the role of AMPK as a heterotrimeric enzyme that senses the energy state of various cell types has been established. Skeletal muscle is a dynamic, plastic tissue that adapts to both functional and metabolic demands of the human body, such as muscle contraction or exercise. With a deliberate focus on AMPK in skeletal muscle, this review places a physiological lens to the association of AMPK and glycogen that has been established biochemically. It discusses that, to date, no in vivo association of AMPK with glycogen has been shown and this is not altered with interventions, either by physiological or biochemical utilisation of glycogen in skeletal muscle. The reason for this is likely due to the persistent phosphorylation of Thr148 in the β-subunit of AMPK which prevents AMPK from binding to carbohydrate domains. This review presents the correlative data that suggests AMPK senses glycogen utilisation through a direct interaction with glycogen, the biochemical data showing that AMPK can bind carbohydrate in vitro, and highlights that in a physiological setting of rodent skeletal muscle, AMPK does not directly bind to glycogen.

Gluconeogenesis and glycogenolysis required in metastatic breast cancer cells.

Metabolic adaptability, including glucose metabolism, enables cells to survive multiple stressful environments. Glycogen may serve as a critical storage depot to provide a source of glucose during times of metabolic demand during the metastatic cascade; therefore, understanding glycogen metabolism is critical. Our goal was to determine mechanisms driving glycogen accumulation and its role in metastatic (MCF10CA1a) compared to nonmetastatic (MCF10A-ras) human breast cancer cells. 13C6-glucose flux analysis in combination with inhibitors of the gluconeogenic pathway via phosphoenolpyruvate carboxykinase (PCK), the anaplerotic enzyme pyruvate carboxylase (PC), and the rate-limiting enzyme of the pentose phosphate pathway (PPP) glucose 6-phosphate dehydrogenase (G6PD). To determine the requirement of glycogenolysis for migration or survival in extracellular matrix (ECM) detached conditions, siRNA inhibition of glycogenolysis (liver glycogen phosphorylase, PYGL) or glycophagy (lysosomal enzyme α-acid glucosidase, GAA) enzymes was utilized. Metastatic MCF10CA1a cells had 20-fold greater glycogen levels compared to non-metastatic MCF10A-ras cells. Most glucose incorporated into glycogen of the MCF10CA1a cells was in the five 13C-containing glucose (M+5) instead of the expected M+6 glycogen-derived glucose moiety, which occurs through direct glucose conversion to glycogen. Furthermore, 13C6-glucose in glycogen was quickly reduced (~50%) following removal of 13C-glucose. Incorporation of 13C6-glucose into the M+5 glucose in the glycogen stores was reduced by inhibition of PCK, with additional contributions from flux through the PPP. Further, inhibition of PC reduced total glycogen content. However, PCK inhibition increased total unlabeled glucose accumulation into glycogen, suggesting an alternative pathway to glycogen accumulation. Inhibition of the rate-limiting steps in glycogenolysis (PYGL) or glycophagy (GAA) demonstrated that both enzymes are necessary to support MCF10CA1a, but not MCF10A-ras, cell migration. GAA inhibition, but not PYGL, reduced viability of MCF10CA1a cells, but not MCF10A-ras, in ECM detached conditions. Our results indicate that increased glycogen accumulation is primarily mediated through the gluconeogenesis pathway and that glycogen utilization is required for both migration and ECM detached survival of metastatic MCF10CA1a cells. These results suggest that glycogen metabolism may play an important role in the progression of breast cancer metastasis.

Global 13C tracing and metabolic flux analysis of intact human liver tissue ex vivo.

Liver metabolism is central to human physiology and influences the pathogenesis of common metabolic diseases. Yet, our understanding of human liver metabolism remains incomplete, with much of current knowledge based on animal or cell culture models that do not fully recapitulate human physiology. Here, we perform in-depth measurement of metabolism in intact human liver tissue ex vivo using global 13C tracing, non-targeted mass spectrometry and model-based metabolic flux analysis. Isotope tracing allowed qualitative assessment of a wide range of metabolic pathways within a single experiment, confirming well-known features of liver metabolism but also revealing unexpected metabolic activities such as de novo creatine synthesis and branched-chain amino acid transamination, where human liver appears to differ from rodent models. Glucose production ex vivo correlated with donor plasma glucose, suggesting that cultured liver tissue retains individual metabolic phenotypes, and could be suppressed by postprandial levels of nutrients and insulin, and also by pharmacological inhibition of glycogen utilization. Isotope tracing ex vivo allows measuring human liver metabolism with great depth and resolution in an experimentally tractable system.

Activation induces shift in nutrient utilization that differentially impacts cell functions in human neutrophils

Neutrophils utilize a variety of metabolic sources to support their crucial functions as the first responders in innate immunity. Here, through in vivo and ex vivo isotopic tracing, we examined the contributions of different nutrients to neutrophil metabolism under specific conditions. Human peripheral blood neutrophils, in contrast to a neutrophil-like cell line, rely on glycogen storage as a major metabolic source under resting state but rapidly switch to primarily using extracellular glucose upon activation with various stimuli. This shift is driven by a substantial increase in glucose uptake, enabled by rapidly increased GLUT1 on cell membrane, that dominates the simultaneous increase in gross glycogen cycling capacity. Shifts in nutrient utilization impact neutrophil functions in a function-specific manner: oxidative burst depends on glucose utilization, whereas NETosis and phagocytosis can be flexibly supported by either glucose or glycogen, and neutrophil migration and fungal control are enhanced by the shift from glycogen utilization to glucose utilization. This work provides a quantitative and dynamic understanding of fundamental features in neutrophil metabolism and elucidates how metabolic remodeling shapes neutrophil functions, which has broad health relevance.

205 An autosomal recessive mutation in PYGM causes myophosphorylase deficiency in composite cattle

Abstract Between 2020 and 2022, eight calves (6 heifers, 2 bulls) in a Nebraska herd (composite Simmental, Red Angus, Gelbvieh) experienced exercise intolerance during extended physical activity. These calves exhibited an inability to keep pace with the rest of the herd, with some eventually succumbing to physical collapse from which they did not recover. Increased creatine kinase, an indication of muscle degeneration, was confirmed in biopsy and necropsy samples. Available sire pedigrees revealed a common paternal ancestor within 2 to 4 generations in all the affected calves. Dam pedigrees were unavailable; however, the herd retained replacement females that occasionally shared common ancestors with breeding bulls. Thus, a de novo autosomal recessive mutation was hypothesized as the cause of exercise intolerance in these calves. Genomic data (100K SNP) from 6 affected calves and 715 herd mates were initially used for a whole genome-wide association study, pinpointing a significant region on chromosome 29. Whole-genome sequencing of 2 affected calves combined with 145 other sequenced cattle led to the identification of a nonsense mutation in the PYGM gene, also located on chromosome 29. The mutation, confirmed to be present in the skeletal muscle transcriptome, was predicted to produce a premature stop codon. The protein product of PYGM, myophosphorylase, has a crucial role in metabolizing glycogen stored within skeletal muscle to generate energy for muscle cells. As a result, the recessive genotype led to greater (P < 0.05) glycogen concentrations in affected calves (n = 2) compared with heterozygous animals (n = 3) and wild-type controls (n = 2). Immunohistochemistry and label-free quantitative proteomics analysis confirmed the absence of the PYGM protein product in skeletal muscle. Myophosphorylase is needed for efficient glycogen utilization, which is crucial for producing high-quality beef. In the 2 affected calves harvested, increased skeletal muscle glycogen persisted postmortem, resulting in increased pH and dark-cutting beef, which is associated with a negative consumer perception and economic losses to the industry. In addition to identifying the cause of exercise intolerance and welfare concerns in these cattle, this study is among the first to identify a specific genetic mutation associated with dark-cutting beef. Carriers of the mutation did not display any discernible differences in meat quality or measures of animal well-being. While cattle heterozygous for the mutation may not immediately impact the beef industry, identifying carriers is paramount for implementing proactive selection and breeding strategies to prevent the production of affected calves.

Role of glycogen metabolism in Clostridioides difficile virulence.

Glycogen plays a vital role as an energy reserve in various bacterial and fungal species. Clostridioides difficile possesses a glycogen metabolism operon that contains genes for both glycogen synthesis and utilization. In our investigation, we focused on understanding the significance of glycogen metabolism in the physiology and pathogenesis of C. difficile. To explore this, we engineered a C. difficile JIR8094 strain lacking glycogen synthesis capability by introducing a group II intron into the glgC gene, the operon's first component. Quantification of intracellular glycogen levels validated the impact of this modification. Interestingly, the mutant strain exhibited a 1.5-fold increase in toxin production compared with the parental strain, without significant changes in the sporulation rate. Our analysis also revealed that wild-type C. difficile spores contained glycogen, whereas spores from the mutant strain lacking stored glycogen showed increased sensitivity to physical and chemical treatments and had a shorter storage life. By suppressing glgP expression, the gene coding for glycogen-phosphorylase, via CRISPRi, we demonstrated that glycogen accumulation but not the utilization is needed for spore resilience in C. difficile. Transmission electron microscopy analysis revealed a significantly lower core/cortex ratio in glgC mutant strain spores. In hamster challenge experiments, both the parental and glgC mutant strains colonized hosts similarly; however, the mutant strain failed to induce infection relapse after antibiotic treatment cessation. These findings highlight the importance of glycogen metabolism in C. difficile spore resilience and suggest its role in disease relapse.IMPORTANCEThis study on the role of glycogen metabolism in Clostridioides difficile highlights its critical involvement in the pathogen's energy management, its pathogenicity, and its resilience. Our results also revealed that glycogen presence in spores is pivotal for their structural integrity and resistance to adverse conditions, which is essential for their longevity and infectivity. Importantly, the inability of the mutant strain to cause infection relapse in hamsters post-antibiotic treatment pinpoints a potential target for therapeutic interventions, highlighting the importance of glycogen in disease dynamics. This research thus significantly advances our understanding of C. difficile physiology and pathogenesis, offering new avenues for combating its persistence and recurrence.

Glycogen pools and utilization during exercise: future implication on glucose regulation.

Glycogen pools and utilization during exercise: future implication on glucose regulation.

CREB-regulated transcription during glycogen synthesis in astrocytes

Glycogen storage, conversion and utilization in astrocytes play an important role in brain energy metabolism. The conversion of glycogen to lactate through glycolysis occurs through the coordinated activities of various enzymes and inhibition of this process can impair different brain processes including formation of long-lasting memories. To replenish depleted glycogen stores, astrocytes undergo glycogen synthesis, a cellular process that has been shown to require transcription and translation during specific stimulation paradigms. However, the detail nuclear signaling mechanisms and transcriptional regulation during glycogen synthesis in astrocytes remains to be explored. In this report, we study the molecular mechanisms of vasoactive intestinal peptide (VIP)-induced glycogen synthesis in astrocytes. VIP is a potent neuropeptide that triggers glycogenolysis followed by glycogen synthesis in astrocytes. We show evidence that VIP-induced glycogen synthesis requires CREB-mediated transcription that is calcium dependent and requires conventional Protein Kinase C but not Protein Kinase A. In parallel to CREB activation, we demonstrate that VIP also triggers nuclear accumulation of the CREB coactivator CRTC2 in astrocytic nuclei. Transcriptome profiles of VIP-induced astrocytes identified robust CREB transcription, including a subset of genes linked to glucose and glycogen metabolism. Finally, we demonstrate that VIP-induced glycogen synthesis shares similar as well as distinct molecular signatures with glucose-induced glycogen synthesis, including the requirement of CREB-mediated transcription. Overall, our data demonstrates the importance of CREB-mediated transcription in astrocytes during stimulus-driven glycogenesis.

Examination of role of the AMP-activated protein kinase (Ampk) signaling pathway during low salinity adaptation in the mud crab, Scylla paramamosain, with reference to glucolipid metabolism

It is known that the marine euryhaline crab, mud crab (Scylla paramamosain), is capable of adapting to low salinity conditions through an innate osmoregulatory system. However, the influence of nutritional conditions during low salinity adaptation has not been fully elucidated. In this study, transcriptome analysis was employed to examine whether low salinity affects the AMP-activated protein kinase (Ampk) signaling pathway, and thereby carbohydrate and lipid metabolism. Further analysis revealed that low salinity activated the expression of P-Ampk and promoted glycolysis and lipolysis, which enhances glycogen and lipid utilization. Nutritional deprivation confirmed that nutrients influenced the survival and osmotic pressure regulation of mud crab under to low salinity via the Ampk signaling pathway. During adaptation to low salinity, carbohydrates were the primary energy source in the initial 7 days, followed by lipids. Further investigation showed that pharmacological stimulation of mechanistic targets in the Ampk signaling pathway using metformin could promote the osmotic pressure regulation of mud crab, confirmed the pivotal role of this pathway in low salinity adaptation. Overall, the present study demonstrated that nutrition, metabolism and osmotic pressure regulation interactively contribute to salinity adaptation in mud crab. Specifically, low salinity induced remodeling of nutritional metabolism homeostasis and promoted glycolipid catabolism, thereby providing energy for osmotic pressure regulation in mud crabs.

Meldonium Supplementation in Professional Athletes: Career Destroyer or Lifesaver?

Meldonium is a substance with known anti-anginal effects demonstrated by numerous studies and human clinical trials; however, it does not possess marketing authorization within the European Union, only in ex-Soviet republics. Since 2016, meldonium has been included by the World Anti-doping Agency (WADA) on the S4 list of metabolic modulators. In performance athletes, meldonium is now considered a doping agent due to its capacity to decrease lactate production during and after exercise, its capability to enhance the storage and utilization of glycogen, and its protective action against oxidative stress. Together, these attributes can significantly improve aerobic endurance, cardiac function, and capacityas well as shorten recovery times (allowing higher intensity training), thereby enhancing performance. The purpose of this review is to highlight the most important mechanisms underlying the protective effect of meldonium against mitochondrial dysfunction (MD), which is responsible for oxidative stress, inflammation, and the cardiac changes known as "athletic heart syndrome."Meldonium acts as an inhibitor of γ-butyrobetaine hydroxylase (BBOX), preventing the de novo synthesis of carnitine and its absorption at the intestinal level via the organic cation/carnitine transporter 2 (OCTN2) and directing the oxidation of fatty acids to the peroxisomes. The decrease in mitochondrial β-oxidation of fatty acids leads to a reduction in lipid peroxidation products that cause oxidative stress and prevent the formation of acyl/acetyl-carnitines involved in numerous pathological disorders. Given the recent findings of the potentially detrimental effects of prolonged high-intensity exercise on cardiovascular health and coronary atherosclerosis, there may be legitimate arguments for the justification of the use of substances likemeldonium as protective supplements for athletes.

Chronic UCN2 Administration Alters Muscle Mass, Exercise Metabolism, and Exercise Capacity in Lean Mice

Urocortin 2 (UCN2) is a member of the corticotropin-releasing hormone (CRH) family and an agonist of the G protein-coupled receptor CRH receptor type 2 (CRHR2), which is highly expressed in skeletal muscle but absent from liver in both rodents and humans. UCN2 overexpression or chronic administration increases muscle mass in both lean and diet-induced obese (DIO) mice and is also believed to increase peripheral insulin sensitivity, reminiscent of the effect of acute exercise. However, how these effects of UCN2 may impact muscle function and exercise capacity remain incompletely understood. We hypothesized that treatment with a long term UCN2 treatment would increase lean and muscle mass and improve aerobic exercise capacity in lean, healthy mice. Lean 10-week-old male C57Bl/6J mice completed treadmill acclimatization and an incremental running test to exhaustion to determine maximal running distance and peak oxygen consumption (VO2). Mice were assigned to sedentary or maximal running groups and were treated with UCN2 for 18 days. After the final dose, body composition was assessed by qNMR. Vehicle- and UCN2-treated mice assigned to the maximal running group completed a second maximal test, and immediately upon completion of exercise, blood glucose was measured, and tissues were collected. Blood glucose and tissues were collected from sedentary vehicle- and UCN2-treated mice in the fed state. UCN2 treatment increased food intake, qNMR lean mass, and individual muscle weights. UCN2-treated mice had reduced maximal running distance, peak VO2, and blood glucose in response to exercise compared to vehicle mice. In addition, UCN2-treated mice had reduced hepatic glycogen in both the sedentary and post maximal exercise states. Gastrocnemius muscle from sedentary UCN2-treated mice had increased glycogen content and reduced phosphorylation of glycogen synthase. Following maximal exercise, UCN2-treated mice had higher gastrocnemius glycogen compared to vehicle mice. This indicated similar total glycogen utilization between treatment groups in response to maximal exercise, despite UCN2-treated mice performing less work. Follow-up studies in sedentary mice demonstrated UCN2 dosing increased phosphorylation of proteins involved in insulin-dependent and -independent glucose uptake in gastrocnemius muscle. These findings indicate that UCN2 affects whole-body and muscle substrate utilization and glucose regulation and signaling which results in increased muscle mass and altered exercise capacity. However, the unpredictability of the effects of UCN2 agonism on these parameters requires much further study. This research was funded by Eli Lilly and Company. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Differential utilisation of subcellular skeletal muscle glycogen pools: a comparative analysis between 1 and 15min of maximal exercise.

In skeletal muscle, glycogen particles are distributed both within and between myofibrils, as well as just beneath the sarcolemma. Their precise localisation may influence their degradation rate. Here, we investigated how exercise at different intensities and durations (1- and 15-min maximal exercise) with known variations in glycogenolytic rate and contribution from anaerobic metabolism affects utilisation of the distinct pools. Furthermore, we investigated how decreased glycogen availability achieved through lowering carbohydrate and energy intake after glycogen-depleting exercise affect the storage of glycogen particles (size, numerical density, localisation). Twenty participants were divided into two groups performing either a 1-min (n=10) or a 15-min (n=10) maximal cycling exercise test. In a randomised, counterbalanced, cross-over design, the exercise tests were performed following short-term consumption of two distinct diets with either high or moderate carbohydrate content (10 vs. 4gkg-1 body mass (BM) day-1) mediating a difference in total energy consumption (240 vs. 138gkg-1 BM day-1). Muscle biopsies from m. vastus lateralis were obtained before and after the exercise tests. Intermyofibrillar glycogen was preferentially utilised during the 1-min test, whereas intramyofibrillar glycogen was preferentially utilised during the 15-min test. Lowering carbohydrate and energy intake after glycogen-depleting exercise reduced glycogen availability by decreasing particle size across all pools and diminishing numerical density in the intramyofibrillar and subsarcolemmal pools. In conclusion, distinct subcellular glycogen pools were differentially utilised during 1-min and 15-min maximal cycling exercise. Additionally, lowered carbohydrate and energy consumption after glycogen-depleting exercise altered glycogen storage by reducing particle size and numerical density, depending on subcellular localisation. KEY POINTS: In human skeletal muscle, glycogen particles are localised in distinct subcellular compartments, referred to as intermyofibrillar, intramyofibrillar and subsarcolemmal pools. The intermyofibrillar and subsarcolemmal pools are close to mitochondria, while the intramyofibrillar pool is at a distance from mitochondria. We show that 1min of maximal exercise is associated with a preferential utilisation of intermyofibrillar glycogen, and, on the other hand, that 15min of maximal exercise is associated with a preferential utilisation of intramyofibrillar glycogen. Furthermore, we demonstrate that reduced glycogen availability achieved through lowering carbohydrate and energy intake after glycogen-depleting exercise is characterised by a decreased glycogen particle size across all compartments, with the numerical density only diminished in the intramyofibrillar and subsarcolemmal compartments. These results suggest that exercise intensity influences the subcellular pools of glycogen differently and that the dietary content of carbohydrates and energy is linked to the size and subcellular distribution of glycogen particles.

Assessing the Potential of Adenosine and L-Theanine as Metabolic Suppressants for Improving Shipping of the New Zealand Scampi (Metanephrops challengeri)

Live crustaceans, especially lobsters, crabs, and shrimp, fetch premium prices in many international seafood markets, especially in parts of Asia. To access these market opportunities, live crustaceans frequently need to be transported over long distances, which can involve prolonged air exposure resulting in elevated stress and increased morbidity and mortality. Interventions which deliver metabolic suppression to live crustaceans during their transport have the potential to improve outcomes from live shipping. In this study, the administration of adenosine (Ado) and L-theanine (L-th) were assessed for metabolic suppression in the New Zealand scampi, Metanephrops challengeri, a deep sea lobster which is highly prized as seafood, and with excellent prospects for supply into premium live seafood markets. The administration to scampi of Ado and L-th in isolation or as a mixture (Ado/L-th), caused a significant decrease in heart rate (HR) with a lasting effect for the 4 hr experimental period. However, this depression of HR did not translate into a systemic downregulation of metabolism, as measured by the key metabolites, i.e., glycogen utilization and the accumulation of lactate and ammonia. The lack of systematic metabolic downregulation would preclude the potential use of Ado and L-th for commercial application in live shipping of crustaceans.

Artemether regulates liver glycogen and lipid utilization through mitochondrial pyruvate oxidation in db/db mice

Artemether regulates liver glycogen and lipid utilization through mitochondrial pyruvate oxidation in db/db mice

The preferential utilization of hepatic glycogen as energy substrates in largemouth bass (Micropterus salmoides) under short-term starvation.

To elucidate the underlying mechanism of the energy metabolism in largemouth bass (Micropterus salmoides), cultured fish (initial body weight: 77.57 ± 0.75 g) in the present study were starved for 0 h, 12 h, 24 h, 48 h, 96 h and 192 h, respectively. The proximate composition analysis showed that short-term starvation induced a significant up-regulation in crude protein proportion in hepatic of cultured fish (P < 0.05). However, short-term starvation significantly decreased the hepatosomatic index and the viscerosomatic index of cultured fish (P < 0.05). The exact hepatic glycogen content in the group starved for 92 h presented remarkable decrease (P < 0.05). Meanwhile, compared with the weight change of lipid and protein (mg) in hepatic (y = 0.0007x2 - 0.2827x + 49.402; y = 0.0013x2 - 0.5666x + 165.31), the decreasing trend of weight in glycogen (mg) was more pronounced (y = 0.0032x2 - 1.817x + 326.52), which suggested the preferential utilization of hepatic glycogen as energy substrates under short-term starvation. Gene expression analysis revealed that the starvation down-regulated the expression of insulin-like growth factor 1 and genes of TOR pathway, such as target of rapamycin (tor) and ribosomal protein S6 (s6) (P < 0.05). In addition, the starvation significantly enhanced expression of lipolysis-related genes, including hormone-sensitive lipase (hsl) and carnitine palmitoyl transferase I (cpt1), but down-regulated lipogenesis as indicated by the inhibited expression of fatty acids synthase (fas), acetyl-CoA carboxylase 1 (acc1) and acetyl-CoA carboxylase 2 (acc2) (P < 0.05). Starvation of 24 h up-regulated the expression of glycolysis genes, glucokinase (gk), phosphofructokinase liver type (pfkl) and pyruvate kinase (pk), and then their expression returned to the normal level. Meanwhile, the expression of gluconeogenesis genes, such as glucose-6-phosphatase catalytic subunit (g6pc), fructose-1,6-bisphosphatase-1 (fbp1) and phosphoenolpyruvate carboxy kinase (pepck), was significantly inhibited with the short-term starvation (P < 0.05). In conclusion, short-term starvation induced an overall decline in growth performance, but it could deplete the hepatic glycogen accumulation and mobilize glycogen for energy effectively.

The N-mannosyltransferase MoAlg9 plays important roles in the development and pathogenicity of Magnaporthe oryzae

Magnaporthe oryzae is the causal agent of rice blast. Glycosylation plays key roles in vegetative growth, development, and infection of M. oryzae. However, several glycosylation-related genes have not been characterized. In this study, we identified a Glyco_transf_22 domain-containing protein, MoAlg9, and found that MoAlg9 is localized to the endoplasmic reticulum (ER). Deletion of MoALG9 significantly affected conidial production, normal appressorium formation, responses to stressors, and pathogenicity of M. oryzae. We also found that the ΔMoalg9 mutant was defective in glycogen utilization, appressorial penetration, and invasive growth in host cells. Moreover, we further demonstrated that MoALG9 regulates the transcription of several target genes involved in conidiation, appressorium formation, and cell-wall integrity. In addition, we found that the Glyco_transf_22 domain is essential for normal MoAlg9 function and localization. We also provide evidence that MoAlg9 is involved in N-glycosylation pathway in M. oryzae. Taken together, these results show that MoAlg9 is important for conidiation, appressorium formation, maintenance of cell wall integrity, and the pathogenesis of M. oryzae.

MoJMJD6, a Nuclear Protein, Regulates Conidial Germination and Appressorium Formation at the Early Stage of Pathogenesis in Magnaporthe oryzae.

In plant-pathogen interactions, Magnaporthe oryzae causes blast disease on more than 50 species of 14 monocot plants, including important crops such as rice, millet, and most 15 recently wheat. M. oryzae is a model fungus for studying plant-microbe interaction, and the main source for fungal pathogenesis in the field. Here we report that MoJMJD6 is required for conidium germination and appressorium formation in M. oryzae. We obtained MoJMJD6 mutants (ΔMojmjd6) using a target gene replacement strategy. The MoJMD6 deletion mutants were delayed for conidium germination, glycogen, and lipid droplets utilization and consequently had decreased virulence. In the ΔMojmjd6 null mutants, global histone methyltransferase modifications (H3K4me3, H3K9me3, H3K27me3, and H3K36me2/3) of the genome were unaffected. Taken together, our results indicated that MoJMJD6 function as a nuclear protein which plays an important role in conidium germination and appressorium formation in the M. oryzae. Our work provides insights into MoJMJD6-mediated regulation in the early stage of pathogenesis in plant fungi.

Pregnane X receptor activation remodels glucose metabolism to promote NAFLD development in obese mice

ObjectiveBoth obesity and exposure to chemicals may induce non-alcoholic fatty liver disease (NAFLD). Pregnane X Receptor (PXR) is a central target of metabolism disrupting chemicals and disturbs hepatic glucose and lipid metabolism. We hypothesized that the metabolic consequences of PXR activation may be modified by existing obesity and associated metabolic dysfunction. MethodsWildtype and PXR knockout male mice were fed high-fat diet to induce obesity and metabolic dysfunction. PXR was activated with pregnenolone-16α-carbonitrile. Glucose metabolism, hepatosteatosis, insulin signaling, glucose uptake, liver glycogen, plasma and liver metabolomics, and liver, white adipose tissue, and muscle transcriptomics were investigated. ResultsPXR activation aggravated obesity-induced liver steatosis by promoting lipogenesis and inhibiting fatty acid disposal. Accordingly, hepatic insulin sensitivity was impaired and circulating alanine aminotransferase level increased. Lipid synthesis was facilitated by increased liver glucose uptake and utilization of glycogen reserves resulting in dissociation of hepatosteatosis and hepatic insulin resistance from the systemic glucose tolerance and insulin sensitivity. Furthermore, glucagon-induced hepatic glucose production was impaired. PXR deficiency did not protect from the metabolic manifestations of obesity, but the liver transcriptomics and metabolomics profiling suggest diminished activation of inflammation and less prominent changes in the overall metabolite profile. ConclusionsObesity and PXR activation by chemical exposure have a synergistic effect on NAFLD development. To support liver fat accumulation the PXR activation reorganizes glucose metabolism that seemingly improves systemic glucose metabolism. This implies that obese individuals, already predisposed to metabolic diseases, may be more susceptible to harmful metabolic effects of PXR-activating drugs and environmental chemicals.

Glycogen availability and pH variation in a medium simulating vaginal fluid influence the growth of vaginal Lactobacillus species and Gardnerella vaginalis

BackgroundGlycogen metabolism by Lactobacillus spp. that dominate the healthy vaginal microbiome contributes to a low vaginal pH (3.5–4.5). During bacterial vaginosis (BV), strict and facultative anaerobes including Gardnerella vaginalis become predominant, leading to an increase in the vaginal pH (> 4.5). BV enhances the risk of obstetrical complications, acquisition of sexually transmitted infections, and cervical cancer. Factors critical for the maintenance of the healthy vaginal microbiome or the transition to the BV microbiome are not well defined. Vaginal pH may affect glycogen metabolism by the vaginal microflora, thus influencing the shift in the vaginal microbiome.ResultsThe medium simulating vaginal fluid (MSVF) supported growth of L. jensenii 62G, L. gasseri 63 AM, and L. crispatus JV-V01, and G. vaginalis JCP8151A at specific initial pH conditions for 30 d. L. jensenii at all three starting pH levels (pH 4.0, 4.5, and 5.0), G. vaginalis at pH 4.5 and 5.0, and L. gasseri at pH 5.0 exhibited the long-term stationary phase when grown in MSVF. L. gasseri at pH 4.5 and L. crispatus at pH 5.0 displayed an extended lag phase over 30 d suggesting inefficient glycogen metabolism. Glycogen was essential for the growth of L. jensenii, L. crispatus, and G. vaginalis; only L. gasseri was able to survive in MSVF without glycogen, and only at pH 5.0, where it used glucose. All four species were able to survive for 15 d in MSVF with half the glycogen content but only at specific starting pH levels – pH 4.5 and 5.0 for L. jensenii, L. gasseri, and G. vaginalis and pH 5.0 for L. crispatus.ConclusionsThese results suggest that variations in the vaginal pH critically influence the colonization of the vaginal tract by lactobacilli and G. vaginalis JCP8151A by affecting their ability to metabolize glycogen. Further, we found that L. jensenii 62G is capable of glycogen metabolism over a broader pH range (4.0–5.0) while L. crispatus JV-V01 glycogen utilization is pH sensitive (only functional at pH 5.0). Finally, our results showed that G. vaginalis JCP8151A can colonize the vaginal tract for an extended period as long as the pH remains at 4.5 or above.