bims-glecem Biomed News
on Glycogen metabolism in exercise, cancer and energy metabolism
Issue of 2022–02–27
twenty-two papers selected by
Dipsikha Biswas, Københavns Universitet



  1. Nutrients. 2022 Feb 18. pii: 862. [Epub ahead of print]14(4):
      The introduction of the needle muscle biopsy technique in the 1960s allowed muscle tissue to be sampled from exercising humans for the first time. The finding that muscle glycogen content reached low levels at exhaustion suggested that the metabolic cause of fatigue during prolonged exercise had been discovered. A special pre-exercise diet that maximized pre-exercise muscle glycogen storage also increased time to fatigue during prolonged exercise. The logical conclusion was that the athlete's pre-exercise muscle glycogen content is the single most important acutely modifiable determinant of endurance capacity. Muscle biochemists proposed that skeletal muscle has an obligatory dependence on high rates of muscle glycogen/carbohydrate oxidation, especially during high intensity or prolonged exercise. Without this obligatory carbohydrate oxidation from muscle glycogen, optimum muscle metabolism cannot be sustained; fatigue develops and exercise performance is impaired. As plausible as this explanation may appear, it has never been proven. Here, I propose an alternate explanation. All the original studies overlooked one crucial finding, specifically that not only were muscle glycogen concentrations low at exhaustion in all trials, but hypoglycemia was also always present. Here, I provide the historical and modern evidence showing that the blood glucose concentration-reflecting the liver glycogen rather than the muscle glycogen content-is the homeostatically-regulated (protected) variable that drives the metabolic response to prolonged exercise. If this is so, nutritional interventions that enhance exercise performance, especially during prolonged exercise, will be those that assist the body in its efforts to maintain the blood glucose concentration within the normal range.
    Keywords:  carbohydrates; diet; endurance; fatigue; fats; hypoglycaemia; liver glycogen; muscle glycogen
    DOI:  https://doi.org/10.3390/nu14040862
  2. Glycoconj J. 2022 Feb 22.
      Glycogen debranching enzyme (GDE) is bifunctional in that it exhibits both 4-α-glucanotransferase and amylo-α-1,6-glucosidase activity at two distinct catalytic sites. GDE converts the phosphorylase-limit biantennary branch [G-G-G-G-(G-G-G-G↔)G-G- residue, where G = D-glucose, hyphens represent α-1,4-glycosidic bonds, and the double-headed arrow represents an α-1,6-glycosidic bond] into a linear maltooligosyl residue, which is then subjected to phosphorylase, and glycogen degradation continues. The prevailing hypothesis regarding the glycogen debranching pathway was that 4-α-glucanotransferase converts the phosphorylase-limit biantennary branch into the G-G-G-G-G-G-G-(G↔)G-G- residue and amylo-α-1,6-glucosidase cleaves the remaining α-1,6-linked G residue. In the present study, we analyzed the substrate specificities of 4-α-glucanotransferase and amylo-α-1,6-glucosidase using fluorogenic biantennary dextrins such as G-G-G-G-(G-G-G-G↔)G-G-GPA (F4/4/2; where GPA = 1-deoxy-1-[(2-pyridyl)amino]-D-glucitol), G-(G-G-G-G↔)G-G-GPA (F1/4/2), and G-G-G-G-G-G-G-(G↔)G-G-GPA (F7/1/2). Contrary to the prevailing hypothesis, the main branch of F4/4/2 was an important donor substrate component of 4-α-glucanotransferase and did not serve as an acceptor substrate. However, when G-G-G-G-G-GPA was added to the mixture, it successfully accepted a maltotriosyl (G3-) residue from F4/4/2. In addition, amylo-α-1,6-glucosidase exhibited strong activity towards G-G-G-G-(G↔)G-G-GPA but weak activity towards F7/1/2. Furthermore, the debranching activity of GDE towards phosphorylase-limit glycogen substantially increased when methyl α-maltooligosides with lengths equal to or greater than that of methyl α-maltopentaoside (G5-OCH3) were added to the enzyme reaction mixture. Based on these results, we propose the following macroscopic debranching pathway: Via 4-α-glucanotransferase, the G3- residue of the donor branch is transferred to a long (n ≥ 5) linear Gn- residue linked to a different branching G residue.
    Keywords:  4-α-glucanotransferase; Amylo-α-1,6-glucosidase; Glycogen debranching enzyme; Glycogen debranching pathway; Phosphorylase-limit dextrin
    DOI:  https://doi.org/10.1007/s10719-022-10046-y
  3. Nutrients. 2022 Feb 18. pii: 856. [Epub ahead of print]14(4):
      High carbohydrate intakes are commonly recommended for athletes of various sports, including strength trainees, to optimize performance. However, the effect of carbohydrate intake on strength training performance has not been systematically analyzed. A systematic literature search was conducted for trials that manipulated carbohydrate intake, including supplements, and measured strength, resistance training or power either acutely or after a diet and strength training program. Studies were categorized as either (1) acute supplementation, (2) exercise-induced glycogen depletion with subsequent carbohydrate manipulation, (3) short-term (2-7 days) carbohydrate manipulation or (4) changes in performance after longer-term diet manipulation and strength training. Forty-nine studies were included: 19 acute, six glycogen depletion, seven short-term and 17 long-term studies. Participants were strength trainees or athletes (39 studies), recreationally active (six studies) or untrained (four studies). Acutely, higher carbohydrate intake did not improve performance in 13 studies and enhanced performance in six studies, primarily in those with fasted control groups and workouts with over 10 sets per muscle group. One study found that a carbohydrate meal improved performance compared to water but not in comparison to a sensory-matched placebo breakfast. There was no evidence of a dose-response effect. After glycogen depletion, carbohydrate supplementation improved performance in three studies compared to placebo, in particular during bi-daily workouts, but not in research with isocaloric controls. None of the seven short-term studies found beneficial effects of carbohydrate manipulation. Longer-term changes in performance were not influenced by carbohydrate intake in 15 studies; one study favored the higher- and one the lower-carbohydrate condition. Carbohydrate intake per se is unlikely to strength training performance in a fed state in workouts consisting of up to 10 sets per muscle group. Performance during higher volumes may benefit from carbohydrates, but more studies with isocaloric control groups, sensory-matched placebos and locally measured glycogen depletion are needed.
    Keywords:  carbohydrate intake; muscle strength; performance; resistance exercise
    DOI:  https://doi.org/10.3390/nu14040856
  4. Int J Biochem Cell Biol. 2022 Feb 22. pii: S1357-2725(22)00029-2. [Epub ahead of print] 106184
      Galactocerebrosidase (GALC) hydrolyses galactose residues from various substrates, including galactosylceramide, psychosine (galactosylsphingosine), and lactosylceramide. Its severe deficiency has been associated with the accumulation of psychosine, a toxic molecule with detergent-like features, which alters membrane structures and signalling pathways, inducing the death of oligodendrocytes and a sequence of events in the nervous system that explain the appearance of many clinical signs typical of Krabbe disease. Nevertheless, new evidence suggests the existence of other possible links among GALC action, myelination, and myelin stability, apart from psychosine release. In this study, we demonstrated that lactosylceramide metabolism is impaired in fibroblasts isolated from patients with Krabbe disease in the absence of psychosine accumulation. This event is responsible for the aberrant and constitutive activation of the AKT/prolin-rich AKT substrate of 40kDa (PRAS40) signalling axis, inducing B cell lymphoma 2 (BCL2) overexpression and glycogen synthase kinase 3 beta (GSK-3β) inhibition. In addition, nuclear factor E2-related factor 2 (NRF2) showed increased nuclear translocation. Due to the relevance of these molecular alterations in neurodegeneration, lactosylceramide increase should be evaluated as a novel marker of Krabbe disease, and because of its significant connections with signalling pathways.
    Keywords:  Krabbe disease; galactocerebrosidase; lactosylceramide
    DOI:  https://doi.org/10.1016/j.biocel.2022.106184
  5. Mol Divers. 2022 Feb 22.
      Effects of allosteric interactions on the classical structure-activity relationship (SAR) and quantitative SAR (QSAR) have been investigated. Apprehending the outliers in SAR and QSAR studies can improve the quality, predictability, and use of QSAR in designing unknown compounds in drug discovery research. We explored allosteric protein-ligand interactions as a possible source of outliers in SAR/QSAR. We used glycogen phosphorylase as an example of a protein that has an allosteric site. Examination of the ligand-bound x-ray crystal structures of glycogen phosphorylase revealed that many inhibitors bound at more than one binding site. The results of QSAR analyses of the inhibitors included a QSAR that recognized an outlier bound at a distinctive allosteric binding site. The case provided an example of constructive use of QSAR identifying outliers with alternative binding modes. Other allosteric QSARs that captured our attention were the inverted parabola/bilinear QSARs. The x-ray crystal structures and the QSAR analyses indicated that the inverted parabola QSARs could be associated with the conformational changes in the allosteric interactions. Our results showed that the normal parabola, as well as the inverted parabola QSARs, can describe the allosteric interactions. Examination of the ligand-bound X-ray crystal structures of glycogen phosphorylase revealed that many inhibitors bound at more than one binding site. The results of QSAR analyses of the inhibitors included a QSAR that recognized an outlier bound at a distinctive allosteric binding site.
    Keywords:  Allosteric interactions; Dual binding modes; Glycogen phosphorylase; Inverted parabola/bilinear QSAR; Quantitative structure–activity relationships (QSAR); Source of outliers; X-ray crystal structure
    DOI:  https://doi.org/10.1007/s11030-021-10365-6
  6. Foods. 2022 Feb 19. pii: 600. [Epub ahead of print]11(4):
      The potential of soft-shelled turtle peptides (STP) against fatigue was evaluated. Mice orally supplemented with STP significantly increased the swimming time until tiredness by 35.4-57.1%. Although not statistically significant, STP increased muscle and thymus mass. In addition, the serum lactate, ammonia, blood urea nitrogen content and creatine kinase activity in STP-fed mice were dramatically decreased when compared to the control group. Furthermore, STP supplementation increased the reserves of liver glycogen and muscle glycogen, thus improved the energy metabolism system of mice. STP treatment contributed to increased superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) activities as well as a decrease in malondialdehyde (MDA), indicating an improvement in oxidative stress protection. The Western blot (WB) results indicated that the STP supplement effectively altered the expression of oxidative stress-related protein by modulating the NRF2/KEAP1 pathway. In summary, STP affected NRF2/KEAP1 levels in skeletal muscle, leading to antioxidant activity and a slower time to exhaustion during exercise.
    Keywords:  KEAP1; NRF2; antifatigue; oxidative stress; soft-shelled turtle peptide
    DOI:  https://doi.org/10.3390/foods11040600
  7. J Vis Exp. 2022 Feb 07.
      With the use of transmission electron microscopy, high-resolution images of fixed samples containing individual muscle fibers can be obtained. This enables quantifications of ultrastructural aspects such as volume fractions, surface area to volume ratios, morphometry, and physical contact sites of different subcellular structures. In the 1970s, a protocol for enhanced staining of glycogen in cells was developed and paved the way for a string of studies on the subcellular localization of glycogen and glycogen particle size using transmission electron microscopy. While most analyses interpret glycogen as if it is homogeneously distributed within the muscle fibers, providing only a single value (e.g., an average concentration), transmission electron microscopy has revealed that glycogen is stored as discrete glycogen particles located in distinct subcellular compartments. Here, the step-by-step protocol from tissue collection to the quantitative determination of the volume fraction and particle diameter of glycogen in the distinct subcellular compartments of individual skeletal muscle fibers is described. Considerations on how to 1) collect and stain tissue specimens, 2) perform image analyses and data handling, 3) evaluate the precision of estimates, 4) discriminate between muscle fiber types, and 5) methodological pitfalls and limitations are included.
    DOI:  https://doi.org/10.3791/63347
  8. J Endocr Soc. 2022 Mar 01. 6(3): bvac008
      Hyperinsulinemia is often observed in obese subjects because of insulin resistance, but it may occur in nonobese subjects with unknown etiology. A 72-year-old man was admitted to our hospital for the examination of hyperinsulinemia, reactive hypoglycemia, and liver dysfunction. The patient's body mass index was 23.7 kg/m2, but he had an elevated visceral fat area (125 cm2). His laboratory data showed mildly elevated liver enzymes, whereas plasma fasting glucose and serum insulin levels were 91 mg/dL and 52.3 μU/mL, respectively. In a 75-g oral glucose tolerance test, the serum insulin level reached the highest value of 1124 μU/mL at 180 minutes. There was no obvious etiology except for mild liver steatosis shown by liver biopsy. We suspected genetic abnormalities related to hyperinsulinemia. We performed whole-exome sequencing (WES) analyses and identified a heterozygous nonsense variant p.R924X in the insulin receptor (INSR) gene, a novel heterozygous missense variant p.V416M in the AKT1 gene, and a novel hemizygous missense variant p.R310Q in the PHKA2 gene, which is the causative gene of hepatic injury as glycogen storage disease type IX. It was speculated that the INSR gene variant, in addition to visceral fat accumulation, was the main cause of hyperinsulinemia and reactive hypoglycemia, and the remaining 2 variants were also partly responsible for hyperinsulinemia. WES analysis revealed candidate gene variants of hyperinsulinemia and hepatic-type glycogenosis. Thus, WES analysis may be a useful tool for clarifying the etiology when unexplained genetic pathophysiological conditions are suspected.
    Keywords:  glycogen storage disease; hyperinsulinemia; insulin receptor gene; whole exome sequencing
    DOI:  https://doi.org/10.1210/jendso/bvac008
  9. Cell Cycle. 2022 Feb 24. 1-12
      Glycogen synthesis kinase-3β (GSK-3β) is a kinase shown to regulate esophageal cancer (EC) progression. However, the significance of GSK-3β in phosphorylation of small kinetochore-associated protein (SKAP) has not been fully characterized. GSK-3β/SKAP expression was analyzed in EC tissues by RT-qPCR. The association between GSK-3β expression and the overall survival was analyzed using the Kaplan-Meier method. Transwell and wound healing assays were performed to assess the effects of GSK-3β/SKAP knockdown on EC cell migration and invasion. By in vitro kinase assay, the SKAP T294 site was identified as a phosphorylated target of GSK-3β. Moreover, we established two cell lines expressing either T294D (phosphor-mimic) or T294A (phosphor-deficiency) SKAP to analyze the effect of SKAP phosphorylation on EC cell invasion, migration, and epithelial-mesenchymal transition (EMT) process. GSK-3β was overexpressed and positively correlated with SKAP levels in EC tissues. Increased GSK-3β expression was associated with EC poor prognosis. Both of GSK-3β knockdown and silencing SKAP decreased EC cell migration and invasion. GSK-3β phosphorylated SKAP protein at Thr294 site. Additionally, a T294D mutant SKAP enhanced cell migration, invasion, and EMT process. Conversely, a T294A mutant SKAP inhibited EC cell malignancy. Meanwhile, cell invasion and migration abilities were inhibited after silencing GSK-3β in EC109-WT, EC109-T294A and EC109-T294D cells. Phosphorylation of SKAP induced by GSK-3β promoted EC cell migration and invasion.
    Keywords:  Esophageal cancer; GSK-3β; SKAP; phosphorylation
    DOI:  https://doi.org/10.1080/15384101.2022.2038847
  10. Environ Sci Pollut Res Int. 2022 Feb 25.
      The most important welding processes used are the gas metal arc (GMA) welding, the tungsten inert gas (TIG) welding, and the manual metal arc (MMA) welding processes. The goal of our investigation was to monitor the distribution of iron (Fe), manganese (Mn), calcium (Ca), and magnesium (Mg) in the lung, spleen, liver, and kidney of mice after inhalation exposure of different welding methods using different steel base materials. The treatment groups were the following: MMA-mild steel, MMA-molybdenum-manganese (MoMn) alloy, TIG-mild steel, and TIG-stainless steel. The samples were taken 24 and 96 h after the treatments. Most importantly, it was found that the Mn concentration in the lung' samples of the MMA-mild steel and the MMA-MoMn groups was increased extremely at both sampling times and in the spleen' samples also. In the TIG groups, the rise of the Mn concentration was only considerable in the lungs and spleens at 24 h, and emerged concentration was found in the liver in 96 h samples. Histopathology demonstrated emerged siderin content in the spleens of the treated animals and in siderin filled macrophages in the lungs mostly in all treated groups. Traces of high-level glycogen retention was found in the MMA groups at both sampling times. Similar glycogen retention in TIG-Ms and TIG stainless group's liver samples and emerged number of vacuoles, especially in the hepatocytes of the TIG-stainless steel 96 h group were also found. The mentioned results raise the consequence that there is a considerable difference in the kinetics of the Mn distribution between the MMA- and the TIG-fume-treated groups. Hence, the result suggests that manganese has a particle-size-dependent toxico-kinetics property. The anomaly of the glycogen metabolism indicates the systemic effect of the welding fumes. Also, the numerous vacuoles mentioned above show a possible liver-specific adverse effect of some components of the TIG-stainless steel welding fumes.
    Keywords:  GMA; MMA; Metals; Nanoparticles; Steel; TIG; Toxico-kinetics; Welding fume
    DOI:  https://doi.org/10.1007/s11356-022-19234-7
  11. Metabolites. 2022 Jan 28. pii: 125. [Epub ahead of print]12(2):
      Secreted protein acidic and rich in cysteine (SPARC) is a matricellular glycoprotein implicated in various functions, including metabolism, tissue regeneration, and functional homeostasis. SPARC/Sparc declines with ageing but increases with exercise. We aim to verify two hypotheses: (1) SPARC deficiency leads to an ageing-like phenotype (metabolic decline, muscle loss, etc.), and (2) SPARC overexpression would mimic exercise, counteract ageing, and improve age-related changes. Our mice experiments are divided into two parts. First, we explore the consequences of Sparc knockout (KO) and compare them to the ageing effects. We also observe the effects of exercise. In the second part, we study the effects of SPARC overexpression and compare them to the exercise benefits. At the end, we make an analysis of the results to point out the analogies between Sparc KO and the ageing-like phenotype on the one hand and make comparisons between SPARC overexpression and exercise in the context of exercise counteracting ageing. The measurements were mainly related to tissue weights, adiposity, metabolism, and muscle strength. The main findings are that Sparc KO reduced glucose tolerance, muscle glucose transporter expression, and abdominal adipose tissue weight but increased glycogen content in the muscle. SPARC overexpression increased muscle strength, muscle mass, and expressions of the muscle glucose transporter and mitochondrial oxidative phosphorylation but lowered the glycemia and the adiposity, especially in males. Collectively, these findings, and the data we have previously reported, show that Sparc KO mice manifest an ageing-like phenotype, whereas SPARC overexpression and exercise generate similar benefits. The benefits are towards counteracting both the SPARC deficiency-induced ageing-like phenotype as well as reversing the age-related changes. The potential applications of these findings are to build/optimize Sparc KO-based animal models of various health conditions and, on the other hand, to develop therapies based on introducing SPARC or targeting SPARC-related pathways to mimic exercise against age-related and metabolic disorders.
    Keywords:  ageing; exercise; metabolism; secreted protein acidic and rich in cysteine (SPARC)
    DOI:  https://doi.org/10.3390/metabo12020125
  12. Biomedicines. 2022 Jan 28. pii: 302. [Epub ahead of print]10(2):
      Pompe disease is an inherited neuromuscular disorder caused by deficiency of the lysosomal enzyme acid alpha-glucosidase (GAA). The most severe form is infantile-onset Pompe disease, presenting shortly after birth with symptoms of cardiomyopathy, respiratory failure and skeletal muscle weakness. Late-onset Pompe disease is characterized by a slower disease progression, primarily affecting skeletal muscles. Despite recent advancements in enzyme replacement therapy management several limitations remain using this therapeutic approach, including risks of immunogenicity complications, inability to penetrate CNS tissue, and the need for life-long therapy. The next wave of promising single therapy interventions involves gene therapies, which are entering into a clinical translational stage. Both adeno-associated virus (AAV) vectors and lentiviral vector (LV)-mediated hematopoietic stem and progenitor (HSPC) gene therapy have the potential to provide effective therapy for this multisystemic disorder. Optimization of viral vector designs, providing tissue-specific expression and GAA protein modifications to enhance secretion and uptake has resulted in improved preclinical efficacy and safety data. In this review, we highlight gene therapy developments, in particular, AAV and LV HSPC-mediated gene therapy technologies, to potentially address all components of the neuromuscular associated Pompe disease pathology.
    Keywords:  Pompe disease; adeno-associated viral vector; enzyme replacement therapy; hematopoietic stem cell; lentiviral vectors
    DOI:  https://doi.org/10.3390/biomedicines10020302
  13. Biomed J. 2022 Feb 17. pii: S2319-4170(22)00028-2. [Epub ahead of print]
       BACKGROUND: K63-linked polyubiquitination of proteins have nonproteolytic functions and regulate the activity of many signal transduction pathways. USP7, a HIF1α deubiquitinase, undergoes K63-linked polyubiquitination under hypoxia. K63-polyubiquitinated USP7 serves as a scaffold to anchor HIF1α, CREBBP, the mediator complex, and the super elongation complex to enhance HIF1α-induced gene transcription. However, the physiological role of K63-polyubiquitinated USP7 remains unknown.
    MATERIALS AND METHODS: Using a Usp7K444R point mutation knock-in mouse strain, we performed immunohistochemistry and standard molecular biological methods to examine the organ defects of liver and kidney in this knock-in mouse strain. Mechanistic studies were performed by using deubiquitination, immunoprecipitation, and quantitative immunoprecipitations (qChIP) assays.
    RESULTS: We observed multiple organ defects, including decreased liver and muscle weight, decreased tibia/fibula length, liver glycogen storage defect, and polycystic kidneys. The underlying mechanisms include the regulation of protein stability and/or modulation of transcriptional activation of several key factors, leading to decreased protein levels of Prr5l, Hnf4α, Cebpα, and Hnf1β. Repression of these crucial factors leads to the organ defects described above.
    CONCLUSIONS: K63-polyubiquitinated Usp7 plays an essential role in the development of multiple organs and illustrates the importance of the process of K63-linked polyubiquitination in regulating critical protein functions.
    Keywords:  K63-linked polyubiquitination; Usp7; glycogen storage; knock-in mouse; polycystic kidney
    DOI:  https://doi.org/10.1016/j.bj.2022.02.002
  14. Mar Drugs. 2022 Jan 21. pii: 91. [Epub ahead of print]20(2):
      Though the relationship between dietary fiber and physical health has been investigated widely, the use of dietary fiber from marine plants has been investigated relatively rarely. The Saccharina japonica byproducts after the production of algin contain a large amount of insoluble polysaccharide, which will cause a waste of resources if ignored. Soluble dietary fiber (SDF)prepared from waste byproducts of Saccharina japonica by alkaline hydrolysis method for the first time had a wrinkled microscopic surface and low crystallinity, which not only significantly reduced liver index, serum levels of aspartate aminotransferase (AST) and alanine amiotransferase (ALT), and liver fat accumulation damage to the livers of obese diabetic mice, but also activated the PI3K/AKT signaling pathway to increase liver glycogen synthesis and glycolysis. By LC-MS/MS employing a Nexera UPLC tandem QE high-resolution mass spectrometer, the 6 potential biomarker metabolites were screened, namely glycerophosphocholine (GPC), phosphocholine (PCho), pantothenic acid, glutathione (GSH), oxidized glutathione (GSSG), and betaine; several pathways of these metabolites were associated with lipid metabolism, glycogen metabolism, and amino acid metabolism in the liver were observed. This study further provided a detailed insight into the mechanisms of SDF from Saccharina japonica byproducts in regulating the livers of obese mice with type 2 diabetes and laid a reliable foundation for the further development and utilization of Saccharina japonica.
    Keywords:  PI3K/AKT; Saccharina japonica; dietary fiber; liver metabolomics
    DOI:  https://doi.org/10.3390/md20020091
  15. J Physiol. 2022 Feb 26.
       KEY FINDINGS: While studies in rodents have highlighted beta2 -agonists as a means to augment insulin sensitivity, these studies utilized beta2 -agonists at doses inapplicable to humans. Herein we show that a 4-week treatment period with daily therapeutic inhalation of beta2 -agonist increases insulin-stimulated whole-body glucose disposal in young healthy lean men. This effect was associated with an increase of lean mass but not with changes in GLUT4 and hexokinase II or basal glycogen content in skeletal muscle nor GLUT4 content in abdominal adipose tissue. These findings suggest that the enhanced insulin-stimulated whole-body glucose disposal induced by a period of beta2 -agonist treatment in humans, at least in part, is attributed to muscle hypertrophy. Our observations extend findings in rodents and highlight the therapeutic potential of beta2 -agonists to enhance the capacity for glucose disposal and whole-body insulin sensitivity, providing important knowledge with potential application in insulin resistance.
    ABSTRACT: Rodent studies highlight enhancement of glucose tolerance and insulin sensitivity as potential clinically relevant effects of chronic beta2 -agonist treatment. However, the doses administered to rodents are incomparable with the therapeutic doses used for humans. Thus, we investigated the physiological effects of prolonged beta2 -agonist treatment at inhaled doses resembling those used in respiratory diseases on insulin-stimulated whole-body glucose disposal and putative mechanisms in skeletal muscle and adipose tissue of healthy men. Utilizing a randomized placebo-controlled parallel-group design, we assigned 21 healthy men to 4 weeks daily inhalation of terbutaline (TER; 4 mg × day-1 , n = 13) or placebo (PLA, n = 8). Before and after treatments, we assessed subjects' whole-body insulin-stimulated glucose disposal and body composition, and collected vastus lateralis muscle and abdominal adipose tissue biopsies. Glucose infusion rate increased by 27% (95% CI: 80 to 238 mg × min-1 , P = 0.001) in TER, whereas no significant changes occurred in PLA (95% CI: -37 to 195 mg × min-1 , P = 0.154). GLUT4 content in muscle or adipose tissue did not change nor hexokinase II content or markers of mitochondrial volume in muscle. Change in lean mass was associated with change in glucose infusion rate in TER (r = 0.59, P = 0.03). Beta2 -agonist treatment in close-to-therapeutic doses may augment whole-body insulin-stimulated glucose disposal in healthy young men and part of the change is likely explained by muscle hypertrophy. These findings highlight the therapeutic potential of beta2 -agonists for improving insulin sensitivity. Abstract figure legend This article is protected by copyright. All rights reserved.
    Keywords:  SABA; adrenergic; adrenoceptor; clenbuterol; glucose transport; insulin sensitivity; muscle hypertrophy; salbutamol
    DOI:  https://doi.org/10.1113/JP282421
  16. Cells. 2022 Feb 18. pii: 727. [Epub ahead of print]11(4):
       BACKGROUND: Common demographic risk factors are identified in colorectal cancer (CRC) and type 2 diabetes mellitus (DM), nevertheless, the molecular link and mechanism for CRC-DM comorbidity remain elusive. Dysregulated glycogen synthase kinase-3 beta under metabolic imbalance is suggested to accelerate CRC pathogenesis/progression via regulating collpasin response mediator protein-2 (CRMP2). Accordingly, roles of CRMP2 in CRC and CRC-DM patients were investigated for elucidating the molecular convergence of CRC and DM.
    METHODS: CRMP2 profile in tumor tissues from CRC and CRC-DM patients was investigated to explore the link between CRC and DM etiology. Meanwhile, molecular mechanism of glucose to regulate CRMP2 profile and CRC characteristics was examined in vitro and in vivo.
    RESULTS: CRMP2 was significantly lower in tumor lesions and associated with advanced tumor stage in CRC-DM patients. Physiological hyperglycemia suppressed CRMP2 expression/activity and augmented malignant characteristics of CRC cells. Hyperglycemia promotes actin de-polymerization, cytoskeleton flexibility and cell proliferation/metastasis by downregulating CRMP2 profile and thus contributes to CRC disease progression.
    CONCLUSIONS: This study uncovers molecular evidence to substantiate and elucidate the link between CRC and T2DM, as well as characterizing the roles of CRMP2 in CRC-DM. Accordingly, altered metabolic adaptations are promising targets for anti-diabetic and cancer strategies.
    Keywords:  CRMP2; colorectal cancer; hyperglycemia; type 2 diabetes mellitus
    DOI:  https://doi.org/10.3390/cells11040727
  17. FASEB J. 2022 03;36(3): e22211
      Metabolic dysfunction and insulin resistance are emerging as hallmarks of cancer and cachexia, and impair cancer prognosis. Yet, the molecular mechanisms underlying impaired metabolic regulation are not fully understood. To elucidate the mechanisms behind cancer-induced insulin resistance in muscle, we isolated extensor digitorum longus (EDL) and soleus muscles from Lewis Lung Carcinoma tumor-bearing mice. Three weeks after tumor inoculation, muscles were isolated and stimulated with or without a submaximal dose of insulin (1.5 nM). Glucose transport was measured using 2-[3 H]Deoxy-Glucose and intramyocellular signaling was investigated using immunoblotting. In soleus muscles from tumor-bearing mice, insulin-stimulated glucose transport was abrogated concomitantly with abolished insulin-induced TBC1D4 and GSK3 phosphorylation. In EDL, glucose transport and TBC1D4 phosphorylation were not impaired in muscles from tumor-bearing mice, while AMPK signaling was elevated. Anabolic insulin signaling via phosphorylation of the mTORC1 targets, p70S6K thr389, and ribosomal-S6 ser235, were decreased by cancer in soleus muscle while increased or unaffected in EDL. In contrast, the mTOR substrate, pULK1 ser757, was reduced in both soleus and EDL by cancer. Hence, cancer causes considerable changes in skeletal muscle insulin signaling that is dependent on muscle-type, which could contribute to metabolic dysregulation in cancer. Thus, the skeletal muscle could be a target for managing metabolic dysfunction in cancer.
    Keywords:  AMPK; Akt; Lewis lung carcinoma; TBC1D4; cachexia; cancer; glucose metabolism; insulin resistance; mTORC1; muscle
    DOI:  https://doi.org/10.1096/fj.202101759R
  18. Pharmaceutics. 2022 Jan 22. pii: 263. [Epub ahead of print]14(2):
      Diabetes mellitus (DM) is a chronic metabolic disorder that threatens human health. Medicinal plants have been a source of wide varieties of pharmacologically active constituents and used extensively as crude extracts or as pure compounds for treating various disease conditions. Thus, the aim of this study is to assess the anti-hyperglycemic and anti-hyperlipidemic effects and the modes of action of the aqueous extracts of the fruits and seeds of Balanites aegyptiaca (B. aegyptiaca) in nicotinamide (NA)/streptozotocin (STZ)-induced diabetic rats. Gas chromatography-mass spectrometry analysis indicated that 3,4,6-tri-O-methyl-d-glucose and 9,12-octadecadienoic acid (Z,Z)- were the major components of the B. aegyptiaca fruit and seed extracts, respectively. A single intraperitoneal injection of STZ (60 mg/kg body weight (b.w.)) 15 min after intraperitoneal NA injection (60 mg/kg b.w.) was administered to induce type 2 DM. After induction was established, the diabetic rats were treated with the B. aegyptiaca fruit and seed aqueous extracts (200 mg/kg b.w./day) via oral gavage for 4 weeks. As a result of the treatments with the B. aegyptiaca fruit and seed extracts, the treated diabetic-treated rats exhibited a significant improvement in the deleterious effects on oral glucose tolerance; serum insulin, and C-peptide levels; liver glycogen content; liver glucose-6-phosphatase and glycogen phosphorylase activities; serum lipid profile; serum free fatty acid level; liver lipid peroxidation; glutathione content and anti-oxidant enzyme (glutathione peroxidase, glutathione-S-transferase, and superoxide dismutase) activities; and the mRNA expression of the adipose tissue expression of the insulin receptor β-subunit. Moreover, the treatment with fruit and seed extracts also produced a remarkable improvement of the pancreatic islet architecture and integrity and increased the islet size and islet cell number. In conclusion, the B. aegyptiaca fruit and seed aqueous extracts exhibit potential anti-hyperglycemic and anti-hyperlipidemic effects, which may be mediated by increasing the serum insulin levels, decreasing insulin resistance, and enhancing the anti-oxidant defense system in diabetic rats.
    Keywords:  Balanitis aegyptiaca; NA/STZ-induced diabetes mellitus; aqueous extracts; fruit; seed
    DOI:  https://doi.org/10.3390/pharmaceutics14020263
  19. Ann Cardiol Angeiol (Paris). 2022 Feb 17. pii: S0003-3928(22)00039-7. [Epub ahead of print]
      Infiltrative cardiomyopathies are abnormal accumulations or depositions of different substances in cardiac tissue leading to its dysfunction, first diastolic, then systolic. The different infiltrative cardiomyopathies are amyloidosis (both light chain amyloidosis and transthyretin amyloidosis variants), lysosomal and glycogen storage disorders (Fabry-Anderson disease), and iron overload (hemochromatosis and thalassemia associated with blood transfusions), as well as inflammatory diseases such as sarcoidosis. We also evoke hypereosinophilic syndrome associated with endomyocardial fibrosis. Echocardiography is the first essential step after interrogatory and clinical examination and may help the cardiologist as a screening tool. Cardiac MRI is the second fundamental step towards the diagnosis especially due to the late gadolinium enhancement and to the T1-mapping. Cardiac amyloidosis diagnosis also requires the use of nuclear imaging. Cardiac CT-Scan may be useful for estimating the amyloid load, identify potential cardiac thrombus and rule out associated coronaropathy.
    Keywords:  Auriculoventricular block; Cardiac CT-Scan; Cardiac MRI; Cardiac amyloidosis; Cardiac stimulation; Echocardiography; Endomyocardial fibrosis; Fabry-Anderson disease; Hemochromatosis; Hypereosinophilic syndrome; Hypertrophic cardiomyopathy; Infiltrative cardiomyopathy; Myocardial scintigraphy; Restrictive cardiomyopathy; Thalassemia
    DOI:  https://doi.org/10.1016/j.ancard.2022.01.001
  20. Metabolites. 2022 Feb 09. pii: 163. [Epub ahead of print]12(2):
      Many cold-acclimated insects accumulate high concentrations of low molecular weight cryoprotectants (CPs) in order to tolerate low subzero temperatures or internal freezing. The sources from which carbon skeletons for CP biosynthesis are driven, and the metabolic reprogramming linked to cold acclimation, are not sufficiently understood. Here we aim to resolve the metabolism of putative CPs by mapping relative changes in concentration of 56 metabolites and expression of 95 relevant genes as larvae of the drosophilid fly, Chymomyza costata transition from a freeze sensitive to a freeze tolerant phenotype during gradual cold acclimation. We found that C. costata larvae may directly assimilate amino acids proline and glutamate from diet to acquire at least half of their large proline stocks (up to 55 µg per average 2 mg larva). Metabolic conversion of internal glutamine reserves that build up in early diapause may explain the second half of proline accumulation, while the metabolic conversion of ornithine and the degradation of larval collagens and other proteins might be two additional minor sources. Next, we confirm that glycogen reserves represent the major source of glucose units for trehalose synthesis and accumulation (up to 27 µg per larva), while the diet may serve as an additional source. Finally, we suggest that interconversions of phospholipids may release accumulated glycero-phosphocholine (GPC) and -ethanolamine (GPE). Choline is a source of accumulated methylamines: glycine-betaine and sarcosine. The sum of methylamines together with GPE and GPC represents approximately 2 µg per larva. In conclusion, we found that food ingestion may be an important source of carbon skeletons for direct assimilation of, and/or metabolic conversions to, CPs in a diapausing and cold-acclimated insect. So far, the cold-acclimation- linked accumulation of CPs in insects was considered to be sourced mainly from internal macromolecular reserves.
    Keywords:  betaine; cryoprotectant metabolites; metabolic pathways; metabolomics; proline; transcriptomics; trehalose
    DOI:  https://doi.org/10.3390/metabo12020163
  21. J Exp Zool A Ecol Integr Physiol. 2022 Feb 21.
      Drosophila melanogaster has been used as the most successful invertebrate model for studying metabolic diseases such as type 2 diabetes (T2D). We induced T2D by feeding Drosophila larvae on a high-sugar diet (HSD). The glucose and trehalose, glycogen, lipid, triglyceride, and protein levels were determined in HSD-fed larvae. Moreover, larval food intake, water content, size, and weight in addition to the development until pupation were observed. Levels of Drosophila insulin-like peptides (DILPs 2, 3, and 5), as well as adipokinetic hormone (AKH), were also determined in HSD-fed larvae by quantitative real-time polymerase chain reaction. The results demonstrated that HSD could induce elevated levels of glucose, trehalose, glycogen, and proteins in larvae. The larvae consumed less food intake and were smaller, lighter, and less developed on HSD than those on the control diet. Moreover, the water content of larvae fed HSD was similar to that fed the control diet. HSD induced higher expression of DILP3 and AKH, confirming hyperglycemia with insulin resistance. In sum, Drosophila offers an appropriate model for quick and inexpensive in vivo experimentation on human metabolic diseases.
    Keywords:  animal model; fruit fly; insulin resistance; metabolic disorder
    DOI:  https://doi.org/10.1002/jez.2580
  22. Front Physiol. 2022 ;13 837697
      Resistance-based blood flow restriction training (BFRT) improves skeletal muscle strength and size. Unlike heavy-load resistance training (HLRT), there is debate as to whether strength adaptations following BFRT interventions can be primarily attributed to concurrent muscle hypertrophy, as the magnitude of hypertrophy is often minor. The present study aimed to investigate the effect of 7 weeks of BFRT and HLRT on muscle strength and hypertrophy. The expression of protein growth markers from muscle biopsy samples was also measured. Male participants were allocated to moderately heavy-load training (HL; n = 9), low-load BFRT (LL + BFR; n = 8), or a control (CON; n = 9) group to control for the effect of time. HL and LL + BFR completed 21 training sessions (3 d.week-1) comprising bilateral knee extension and knee flexion exercises (HL = 70% one-repetition maximum (1-RM), LL + BFR = 20% 1-RM + blood flow restriction). Bilateral knee extension and flexion 1-RM strength were assessed, and leg muscle CSA was measured via peripheral quantitative computed tomography. Protein growth markers were measured in vastus lateralis biopsy samples taken pre- and post the first and last training sessions. Biopsy samples were also taken from CON at the same time intervals as HL and LL + BFR. Knee extension 1-RM strength increased in HL (19%) and LL + BFR (19%) but not CON (2%; p < 0.05). Knee flexion 1-RM strength increased similarly between all groups, as did muscle CSA (50% femur length; HL = 2.2%, LL + BFR = 3.0%, CON = 2.1%; TIME main effects). 4E-BP1 (Thr37/46) phosphorylation was lower in HL and LL + BFR immediately post-exercise compared with CON in both sessions (p < 0.05). Expression of other growth markers was similar between groups (p > 0.05). Overall, BFRT and HLRT improved muscle strength and size similarly, with comparable changes in intramuscular protein growth marker expression, both acutely and chronically, suggesting the activation of similar anabolic pathways. However, the low magnitude of muscle hypertrophy was not significantly different to the non-training control suggesting that strength adaptation following 7 weeks of BFRT is not driven by hypertrophy, but rather neurological adaptation.
    Keywords:  growth markers; hypertrophy; skeletal muscle; strength; vascular occlusion
    DOI:  https://doi.org/10.3389/fphys.2022.837697