bims-glecem 2022-09-11 papers

bims-glecem

Biomed News

on Glycogen metabolism in exercise, cancer and energy metabolism

Issue of 2022–09–11
fiveteen papers selected by
Dipsikha Biswas, Københavns Universitet

A Mouse Model of Glycogen Storage Disease Type IX-Beta: A Role for Phkb in Glycogenolysis.
In situ mass spectrometry imaging reveals heterogeneous glycogen stores in human normal and cancerous tissues.
The fragility of liver glycogen from humans with type 2 diabetes: A pilot study.
[Genetic analysis of a child with glycogen storage disease type IXa due to a novel variant in PHKA2 gene].
Assessment of auditory functions in patients with hepatic glycogen storage diseases.
Pathomorphogenesis of Glycogen-Ground Glass Hepatocytic Inclusions (Polyglucosan Bodies) in Children after Liver Transplantation.
Inhibition of monocarboxylate transporters (MCT) 1 and 4 reduces exercise capacity in mice.
Recurrent hypoglycemia increases hepatic gluconeogenesis without affecting glycogen metabolism or systemic lipolysis in rat.
Silencing of Glycogen Synthase Kinase 3 Significantly Inhibits Chitin and Fatty Acid Metabolism in Asian Citrus Psyllid, Diaphorina citri.
Coronarin A modulated hepatic glycogen synthesis and gluconeogenesis via inhibiting mTORC1/S6K1 signaling and ameliorated glucose homeostasis of diabetic mice.
Sexual dimorphism in response to repetitive bouts of acute aerobic exercise in rodents with type 1 diabetes mellitus.
Sacubitril/valsartan combination enhanced cardiac glycophagy and prevented the progression of murine diabetic cardiomyopathy.
Human adaptation to immobilization: Novel insights of impacts on glucose disposal and fuel utilization.
Vasorin Deletion in C57BL/6J Mice Induces Hepatocyte Autophagy through Glycogen-Mediated mTOR Regulation.
The earliest enzyme replacement for infantile-onset Pompe disease in Japan.

Int J Mol Sci. 2022 Sep 01. pii: 9944. [Epub ahead of print]23(17):

A Mouse Model of Glycogen Storage Disease Type IX-Beta: A Role for Phkb in Glycogenolysis.

Charles J Arends, Lane H Wilson, Ana Estrella, Oh Sung Kwon, David A Weinstein, Young Mok Lee.

  Glycogen storage disease type IX (GSD-IX) constitutes nearly a quarter of all GSDs. This ketotic form of GSD is caused by mutations in phosphorylase kinase (PhK), which is composed of four subunits (α, β, γ, δ). PhK is required for the activation of the liver isoform of glycogen phosphorylase (PYGL), which generates free glucose-1-phosphate monomers to be used as energy via cleavage of the α -(1,4) glycosidic linkages in glycogen chains. Mutations in any of the PhK subunits can negatively affect the regulatory and catalytic activity of PhK during glycogenolysis. To understand the pathogenesis of GSD-IX-beta, we characterized a newly created PHKB knockout (Phkb-/-) mouse model. In this study, we assessed fasting blood glucose and ketone levels, serum metabolite concentrations, glycogen phosphorylase activity, and gene expression of gluconeogenic genes and fibrotic genes. Phkb-/- mice displayed hepatomegaly with lower fasting blood glucose concentrations. Phkb-/- mice showed partial liver glycogen phosphorylase activity and increased sensitivity to pyruvate, indicative of partial glycogenolytic activity and upregulation of gluconeogenesis. Additionally, gene expression analysis demonstrated increased lipid metabolism in Phkb-/- mice. Gene expression analysis and liver histology in the livers of old Phkb-/- mice (>40 weeks) showed minimal profibrogenic features when analyzed with age-matched wild-type (WT) mice. Collectively, the Phkb-/- mouse recapitulates mild clinical features in patients with GSD-IX-beta. Metabolic and molecular analysis confirmed that Phkb-/- mice were capable of sustaining energy homeostasis during prolonged fasting by using partial glycogenolysis, increased gluconeogenesis, and potentially fatty acid oxidation in the liver.

Keywords:  glucose; glycogenolysis; hepatomegaly; hypoglycemia; ketosis

DOI:  https://doi.org/10.3390/ijms23179944
EMBO Mol Med. 2022 Sep 05. e16029

In situ mass spectrometry imaging reveals heterogeneous glycogen stores in human normal and cancerous tissues.

Lyndsay E A Young, Lindsey R Conroy, Harrison A Clarke, Tara R Hawkinson, Kayli E Bolton, William C Sanders, Josephine E Chang, Madison B Webb, Warren J Alilain, Craig W Vander Kooi, Richard R Drake, Douglas A Andres, Tom C Badgett, Lars M Wagner, Derek B Allison, Ramon C Sun, Matthew S Gentry.

  Glycogen dysregulation is a hallmark of aging, and aberrant glycogen drives metabolic reprogramming and pathogenesis in multiple diseases. However, glycogen heterogeneity in healthy and diseased tissues remains largely unknown. Herein, we describe a method to define spatial glycogen architecture in mouse and human tissues using matrix-assisted laser desorption/ionization mass spectrometry imaging. This assay provides robust and sensitive spatial glycogen quantification and architecture characterization in the brain, liver, kidney, testis, lung, bladder, and even the bone. Armed with this tool, we interrogated glycogen spatial distribution and architecture in different types of human cancers. We demonstrate that glycogen stores and architecture are heterogeneous among diseases. Additionally, we observe unique hyperphosphorylated glycogen accumulation in Ewing sarcoma, a pediatric bone cancer. Using preclinical models, we correct glycogen hyperphosphorylation in Ewing sarcoma through genetic and pharmacological interventions that ablate in vivo tumor growth, demonstrating the clinical therapeutic potential of targeting glycogen in Ewing sarcoma.

Keywords:  Ewing sarcoma; MALDI imaging; glycogen; glycogen storage disease; spatial metabolism

DOI:  https://doi.org/10.15252/emmm.202216029
Int J Biol Macromol. 2022 Sep 06. pii: S0141-8130(22)01922-5. [Epub ahead of print]221 83-90

The fragility of liver glycogen from humans with type 2 diabetes: A pilot study.

Ziyi Wang, Xiaobo Min, Zhenxia Hu, Mitchell A Sullivan, Yong Tang, Liang Wang, Robert G Gilbert, Chen Shi, Bin Deng.

  Liver glycogen is a highly branched glucose polymer found as β particles (~20 nm in diameter), which can bind together into larger composite α particles. Hepatic α particles have been shown to be structurally fragile (breaking up into smaller particles in certain solvents) in mouse models of diabetes; if occurring in vivo, the resulting small glycogen particles could exacerbate the poor blood-sugar homeostasis characteristic of the disease. Here we tested if this α-particle fragility also occurred in liver glycogen obtained from humans with diabetes. It was found that liver glycogen from diabetic humans was indeed more fragile than from non-diabetic humans, which was also seen in the mouse experiments we ran in parallel. Proteomic analysis revealed three candidate proteins from differentially expressed glycogen proteins (Diabetes/ Non-diabetes) in both human and mouse groups. Identifying these proteins may give clues to the binding mechanism that holds together α particles together, which, being different in diabetic glycogen, is relevant to diabetes prevention and management.

Keywords:  Chain-length distributions; Diabetes; Glycogen; Size exclusion chromatography; Transmission electron microscopy

DOI:  https://doi.org/10.1016/j.ijbiomac.2022.08.212
Zhonghua Yi Xue Yi Chuan Xue Za Zhi. 2022 Sep 10. 39(9): 988-991

[Genetic analysis of a child with glycogen storage disease type IXa due to a novel variant in PHKA2 gene].

Ganye Zhao, Wenzhe Si, Xuechao Zhao, Li'na Liu, Conghui Wang, Xiangdong Kong.

OBJECTIVE: To explore the genetic etiology of a patient with glycogen storage diseases.
METHODS: Clinical data of child and his parents were collected. The genes associated with glycogen storage diseases were subjected to high-throughput sequencing to screen the variants. Candidate variant was validated by Sanger sequencing. Pathogenicity of the variant was predicted by bioinformatic analysis.
RESULTS: High-throughput sequencing results showed that the boy has carried a hemizygous c.749C>T (p.S250L) variant of the PHKA2 gene. Sanger sequencing verified the results and confirmed that it was inherited from his mother. This variant was unreported previously and predicted to be pathogenic by bioinformatic analysis.
CONCLUSION: The patient was diagnosed with glycogen storage disease type IXa due to a novel c.749C>T (p.S250L) hemizygous variant of the PHKA2 gene. High-throughput sequencing can facilitate timely and accurate differential diagnosis of glycogen storage disease type IXa.

DOI: https://doi.org/10.3760/cma.j.cn511374-20210610-00495
Turk J Pediatr. 2022 ;pii: 2472. [Epub ahead of print]64(4): 658-670

Assessment of auditory functions in patients with hepatic glycogen storage diseases.

Merve Emecen Şanlı, Nuriye Yıldırım Gökay, Hakan Tutar, Bülent Gündüz, Ekin Özsaydı, Ayşe Kılıç, Aslı İnci, İlyas Okur, Fatih Ezgü, Leyla Tümer.

   BACKGROUND: Hepatic glycogen storage diseases are a group of diseases manifesting mainly with hypoglycemia and hepatomegaly. The patients require frequent daytime and nocturnal feedings. Hypoglycemia may cause sensorineural hearing loss and nocturnal feeding is a risk factor for the development of gastroesophageal reflux that may cause chronic otitis media and hearing loss consequently. We aimed to determine the prevalence and characteristics of hearing loss in hepatic glycogen storage diseases.
METHODS: A total of 24 patients with hepatic glycogen storage disease (15 glycogen storage disease type I and 9 non type I) and 24 age/sex matched healthy controls were enrolled in the study. Pure tone audiometer, immitansmetry, acoustic reflex measurement, otoacoustic emission test (OAE) and auditory brainstem response (ABR) tests were applied to all participants.
RESULTS: Hearing loss was determined in 17/24 patients (12 glycogen storage disease type I and 5 non type I) with pure tone audiometer. Interpretation of all the findings revealed a total of 8 patients had conductive and 9 had mixed hearing loss. All parameters were significantly different than the control group.
CONCLUSIONS: This is the first study to comprehensively assess the auditory functions of patients with hepatic glycogen storage disease. Audiological findings determined a significantly increased prevalence of conductive/ mixed type hearing loss in the patient group which is a new finding in the literature. Further studies with extended patient numbers are required to enlighten the underlying pathophysiology.

Keywords:  auditory function; glycogen storage disease; hearing loss; hypoglycemia; nocturnal feeding

DOI:  https://doi.org/10.24953/turkjped.2022.142
Int J Mol Sci. 2022 Sep 02. pii: 9996. [Epub ahead of print]23(17):

Pathomorphogenesis of Glycogen-Ground Glass Hepatocytic Inclusions (Polyglucosan Bodies) in Children after Liver Transplantation.

Francesco Callea, Paola Francalanci, Chiara Grimaldi, Francesca Diomedi Camassei, Rita Devito, Fabio Facchetti, Rita Alaggio, Emanuele Bellacchio.

  Seventeen out of 764 liver biopsies from transplanted (Tx) livers in children showed glycogen-ground glass (GGG) hepatocytic inclusions. The inclusions were not present in pre-Tx or in the explanted or donor's liver. Under the electron microscope (EM), the stored material within the cytosol appeared as non-membrane-bound aggregates of electron-lucent globoid or fibrillar granules, previously described as abnormally structured glycogen and identified as Polyglucosan bodies (PB). The appearance of GGG in our children was analogous to that of PB-GGG occurring in a number of congenital diseases due to gene mutations such as Lafora's d., Andersen's d., Adult Polyglucosan Body Disease and glycogenin deficiency. The same type of GGG was previously reported in the liver of patients undergoing transplants, immunosuppressive or antiblastic treatment. To explore the potential mechanism of GGG formation, we examined whether the drugs after whose treatment this phenomenon was observed could have a role. By carrying out molecular docking, we found that such drugs somehow present a high binding affinity for the active region of glycogenin, implicating that they can inactivate the protein, thus preventing its interaction with glycogen synthase (GS), as well as the maturation of the nascent glycogen towards gamma, beta or alfa glycogen granules. We could also demonstrate that PG inclusions consist of a complex of PAS positive material (glycogen) and glycogen-associated proteins, i.e., glicogenin-1 and -2 and ubiquitin. These features appear to be analogous to congenital GGG, suggesting that, in both cases, they result from the simultaneous dysregulation of glycogen synthesis and degradation. Drug-induced GGG appear to be toxic to the cell, despite their reversibility.

Keywords:  drugs; glycogen-ground glass; hepatocytes; polyglucosan bodies

DOI:  https://doi.org/10.3390/ijms23179996
Physiol Rep. 2022 Sep;10(17): e15457

Inhibition of monocarboxylate transporters (MCT) 1 and 4 reduces exercise capacity in mice.

Yu Kitaoka, Kenya Takahashi, Hideo Hatta.

  The concept of lactate shuttle is widely accepted in exercise physiology. Lactate transport is mediated by monocarboxylate transporters (MCT), which enable cells to take up and release lactate. However, the role of lactate during exercise has not yet been fully elucidated. In this study, we investigated the effects of lactate transport inhibition on exercise capacity and metabolism in mice. Here, we demonstrated that MCT1 inhibition by α-cyano-4-hydroxycinnamate administration (4-CIN, 200 mg/g of body weight) reduced the treadmill running duration at 20 m/min. The administration of 4-CIN increased the blood lactate concentration immediately after exercise. With matched exercise duration, the muscle lactate concentration was higher while muscle glycogen content was lower in 4-CIN-administered mice. Further, we showed that MCT4 inhibition by bindarit administration (50 mg/kg of body weight) reduced the treadmill running duration at 40 m/min. Bindarit administration increased the muscle lactate but did not alter the blood lactate and glucose concentrations, as well as muscle glycogen content, immediately after exercise. A negative correlation was observed between exercise duration at 40 m/min and muscle lactate concentration immediately after exercise. Our results suggest that lactate transport via MCT1 and MCT4 plays a pivotal role in sustaining exercise.

Keywords:  MCT; exercise; lactate; skeletal muscle

DOI:  https://doi.org/10.14814/phy2.15457
Metabolism. 2022 Sep 03. pii: S0026-0495(22)00188-3. [Epub ahead of print]136 155310

Recurrent hypoglycemia increases hepatic gluconeogenesis without affecting glycogen metabolism or systemic lipolysis in rat.

Zejian Liu, Lingyu Zhang, Chen Qian, Ying Zhou, Qiuyu Yu, Jiaqi Yuan, Yunfan Lv, Leheng Zhang, Xiaoai Chang, Yangyang Li, Yu Liu.

   INTRODUCTION: Recurrent hypoglycemia (RH) impairs secretion of counterregulatory hormones. Whether and how RH affects responses within metabolically important peripheral organs to counterregulatory hormones are poorly understood.
OBJECTIVE: To study the effects of RH on metabolic pathways associated with glucose counterregulation within liver, white adipose tissue and skeletal muscle.
METHODS: Using a widely adopted rodent model of 3-day recurrent hypoglycemia, we first checked expression of counterregulatory hormone G-protein coupled receptors (GPCRs), their inhibitory regulators and downstream enzymes catalyzing glycogen metabolism, gluconeogenesis and lipolysis by qPCR and western blot. Then, we examined epinephrine-induced phosphorylation of PKA substrates to validate adrenergic sensitivity in each organ. Next, we measured hepatic and skeletal glycogen content, degree of breakdown by epinephrine and abundance of phosphorylated glycogen phosphorylase under hypoglycemia and that of phosphorylated glycogen synthase during recovery to evaluate glycogen turnover. Further, we performed pyruvate and lactate tolerance tests to assess gluconeogenesis. Additionally, we measured circulating FFA and glycerol to check lipolysis. The abovementioned studies were repeated in streptozotocin-induced diabetic rat model. Finally, we conducted epinephrine tolerance test to investigate systemic glycemic excursions to counterregulatory hormones. Saline-injected rats served as controls.
RESULTS: RH increased counterregulatory hormone GPCR signaling in liver and epidydimal white adipose tissue (eWAT), but not in skeletal muscle. For glycogen metabolism, RH did not affect total content or epinephrine-stimulated breakdown in liver and skeletal muscle. Although RH decreased expression of phosphorylated glycogen synthase 2, it did not affect hepatic glycogen biosynthesis during recovery from hypoglycemia or after fasting-refeeding. For gluconeogenesis, RH upregulated fructose 1,6-bisphosphatase 1 and monocarboxylic acid transporter 1 that imports lactate as precursor, resulting in a lower blood lactate profile during hypoglycemia. In agreement, RH elevated fasting blood glucose and caused higher glycemic excursions during pyruvate tolerance test. For lipolysis, RH did not affect circulating levels of FFA and glycerol after overnight fasting or upon epinephrine stimulation. Interestingly, RH upregulated the trophic fatty acid transporter FATP1 and glucose transporter GLUT4 to increase lipogenesis in eWAT. These aforementioned changes of gluconeogenesis, lipolysis and lipogenesis were validated in streptozotocin-diabetic rats. Finally, RH increased insulin sensitivity to accelerate glucose disposal, which was attributable to upregulated visceral adipose GLUT4.
CONCLUSIONS: RH caused metabolic adaptations related to counterregulation within peripheral organs. Specifically, adrenergic signaling was enhanced in liver and visceral fat, but not in skeletal muscle. Glycogen metabolism remained unchanged. Hepatic gluconeogenesis was augmented. Systemic lipolysis was unaffected, but visceral lipogenesis was enhanced. Insulin sensitivity was increased. These findings provided insights into mechanisms underlying clinical problems associated with intensive insulin therapy, such as high gluconeogenic flux and body weight gain.

Keywords:  Adrenergic sensitivity; Gluconeogenesis; Glycogen; Insulin sensitivity; Monocarboxylic acid transporter; Recurrent hypoglycemia

DOI:  https://doi.org/10.1016/j.metabol.2022.155310
Int J Mol Sci. 2022 Aug 25. pii: 9654. [Epub ahead of print]23(17):

Silencing of Glycogen Synthase Kinase 3 Significantly Inhibits Chitin and Fatty Acid Metabolism in Asian Citrus Psyllid, Diaphorina citri.

Jin-Bo Zhang, Zhan-Jun Lu, Hai-Zhong Yu.

  Glycogen is a predominant carbohydrate reserve in various organisms, which provides energy for different life activities. Glycogen synthase kinase 3 (GSK3) is a central player that catalyzes glucose and converts it into glycogen. In this study, a GSK3 gene was identified from the D. citri genome database and named DcGSK3. A reverse transcription quantitative PCR (RT-qPCR) analysis showed that DcGSK3 was expressed at a high level in the head and egg. The silencing of DcGSK3 by RNA interference (RNAi) led to a loss-of-function phenotype. In addition, DcGSK3 knockdown decreased trehalase activity, glycogen, trehalose, glucose and free fatty acid content. Moreover, the expression levels of the genes associated with chitin and fatty acid synthesis were significantly downregulated after the silencing of DcGSK3. According to a comparative transcriptomics analysis, 991 differentially expressed genes (DEGs) were identified in dsDcGSK3 groups compared with dsGFP groups. A KEGG enrichment analysis suggested that these DEGs were primarily involved in carbon and fatty acid metabolism. The clustering analysis of DEGs further confirmed that chitin and fatty acid metabolism-related DEGs were upregulated at 24 h and were downregulated at 48 h. Our results suggest that DcGSK3 plays an important role in regulating the chitin and fatty acid metabolism of D. citri.

Keywords:  DcGSK3; Diaphorina citri; RNA interference; chitin; fatty acid; transcriptome sequencing

DOI:  https://doi.org/10.3390/ijms23179654
Acta Pharmacol Sin. 2022 Sep 09.

Coronarin A modulated hepatic glycogen synthesis and gluconeogenesis via inhibiting mTORC1/S6K1 signaling and ameliorated glucose homeostasis of diabetic mice.

Su-Ling Huang, Wei Xie, Yang-Liang Ye, Jia Liu, Hui Qu, Yu Shen, Ti-Fei Xu, Zhuo-Hui Zhao, Yu Shi, Jian-Hua Shen, Ying Leng.

  Promotion of hepatic glycogen synthesis and inhibition of hepatic glucose production are effective strategies for controlling hyperglycemia in type 2 diabetes mellitus (T2DM), but agents with both properties were limited. Herein we report coronarin A, a natural compound isolated from rhizomes of Hedychium gardnerianum, which simultaneously stimulates glycogen synthesis and suppresses gluconeogenesis in rat primary hepatocytes. We showed that coronarin A (3, 10 μM) dose-dependently stimulated glycogen synthesis accompanied by increased Akt and GSK3β phosphorylation in rat primary hepatocytes. Pretreatment with Akt inhibitor MK-2206 (2 μM) or PI3K inhibitor LY294002 (10 μM) blocked coronarin A-induced glycogen synthesis. Meanwhile, coronarin A (10 μM) significantly suppressed gluconeogenesis accompanied by increased phosphorylation of MEK, ERK1/2, β-catenin and increased the gene expression of TCF7L2 in rat primary hepatocytes. Pretreatment with β-catenin inhibitor IWR-1-endo (10 μM) or ERK inhibitor SCH772984 (1 μM) abolished the coronarin A-suppressed gluconeogenesis. More importantly, we revealed that coronarin A activated PI3K/Akt/GSK3β and ERK/Wnt/β-catenin signaling via regulation of a key upstream molecule IRS1. Coronarin A (10, 30 μM) decreased the phosphorylation of mTOR and S6K1, the downstream target of mTORC1, which further inhibited the serine phosphorylation of IRS1, and subsequently increased the tyrosine phosphorylation of IRS1. In type 2 diabetic ob/ob mice, chronic administration of coronarin A significantly reduced the non-fasting and fasting blood glucose levels and improved glucose tolerance, accompanied by the inhibited hepatic mTOR/S6K1 signaling and activated IRS1 along with enhanced PI3K/Akt/GSK3β and ERK/Wnt/β-catenin pathways. These results demonstrate the anti-hyperglycemic effect of coronarin A with a novel mechanism by inhibiting mTORC1/S6K1 to increase IRS1 activity, and highlighted coronarin A as a valuable lead compound for the treatment of T2DM.

Keywords:  IRS1; coronarin A; gluconeogenesis; glycogen synthesis; mTORC1/S6K1 pathway; type 2 diabetes mellitus

DOI:  https://doi.org/10.1038/s41401-022-00985-5
PLoS One. 2022 ;17(9): e0273701

Sexual dimorphism in response to repetitive bouts of acute aerobic exercise in rodents with type 1 diabetes mellitus.

Jordan C Larocque, Silar Gardy, Mitchell Sammut, David P McBey, C W James Melling.

The purpose of this study was to examine sex-specific differences in the blood glucose (BG) response to recurrent aerobic exercise in type 1 diabetes rats. Specifically, we examined the role of peak estrogen (E2) concentrations during proestrus on BG response to prolonged repetitive aerobic exercise. To do so, nineteen Sprague-Dawley rats were assigned to four exercised groups: control female (CXF; n = 5), control male (CXM; n = 5), diabetic female (DXF, n = 5) and diabetic male (DXM, n = 4). Diabetes was induced in DX groups via subcutaneous multiple injections of low dose streptozotocin (20mg/day for 7 days). After four days of exercise, muscle and liver glycogen content, liver gluconeogenic enzyme content, muscle Beta oxidation activity and BG responses to exercise were compared. The final bout of exercise took place during proestrus when E2 concentrations were at their highest in the female rats. During days 1-3 DXM had significantly lower BG concentrations during exercise than DXF. While both T1DM and non-T1DM females demonstrated higher hepatic G6Pase expression and muscle beta oxidation activity levels on day 4 exercise, no differences in BG response between the male and female T1DM rats were evident. Further, no differences in liver and muscle glycogen content following day 4 of exercise were seen between the sexes. These results would suggest that heightened E2 levels during proestrus may not be an important factor governing glucose counter regulatory response to exercise in female T1DM rats. Rather, the pre-exercise blood glucose levels are likely to be a large determinant of the blood glucose response to exercise in both male and female rats.

DOI: https://doi.org/10.1371/journal.pone.0273701
Biomed Pharmacother. 2022 Sep;pii: S0753-3322(22)00771-5. [Epub ahead of print]153 113382

Sacubitril/valsartan combination enhanced cardiac glycophagy and prevented the progression of murine diabetic cardiomyopathy.

Dina Salem Abdelaziz Elshenawy, Nehal Mohammed Ramadan, Vivian Boshra Abdo, Rehab Hamdy Ashour.

   BACKGROUND: Diabetic cardiomyopathy (DCM) is linked to disturbance in cardiac glucose handling and increased cardiac glycogen storage. This study tested the potential role of sacubitril/valsartan on the progression of DCM in high fat diet (HFD)/streptozotocin (STZ)-induced type 2 diabetic rats compared to valsartan alone, including their effects on the cardiac glycophagy process.
MATERIALS AND METHODS: Rats were fed on HFD for 6 weeks followed by single low-dose STZ (35 mg/kg). After confirming hyperglycemia, diabetic rats were continued on HFD and divided into three subgroups: Untreated-diabetic, Valsartan-treated diabetic and Sacubitril/valsartan-treated diabetic groups; in addition to a control group. Changes in ECG, blood glucose, serum insulin, lipid profile, and Homeostasis model of assessment of insulin resistance (HOMA-IR) were assessed and the degree of cardiac fibrosis was examined. Cardiac glycogen content and glycophagy process were evaluated.
RESULTS: Sacubitril/valsartan administration to diabetic rats resulted in improvement of metabolic changes more than valsartan alone. Also, sacubitril/valsartan effectively prevented diabetes-associated cardiac hypertrophy, QTc prolongation, and fibrosis. Finally, cardiac glycogen concentrations in diabetic rats were decreased by sacubitril/valsartan combination, coupled with significant induction of glycophagy process in the diabetic rats' heart.
CONCLUSION: Sacubitril/valsartan therapy provides a more favorable metabolic and cardioprotective response compared to valsartan alone in a rat model of DCM. These findings may be due to a direct cardioprotective impact of sacubitril/valsartan and secondary beneficial effects of improved hyperglycemia and dyslipidemia. In addition, these beneficial cardiac effects could be attributed to the induction of the glycophagy process and alleviating cardiac glycogen overload.

Keywords:  Diabetes mellitus; Diabetic cardiomyopathy; Glycogen; Glycophagy; Heart failure; Sacubitril/valsartan

DOI:  https://doi.org/10.1016/j.biopha.2022.113382
J Cachexia Sarcopenia Muscle. 2022 Sep 04.

Human adaptation to immobilization: Novel insights of impacts on glucose disposal and fuel utilization.

Natalie F Shur, Elizabeth J Simpson, Hannah Crossland, Prince K Chivaka, Despina Constantin, Sally M Cordon, Dumitru Constantin-Teodosiu, Francis B Stephens, Dileep N Lobo, Nate Szewczyk, Marco Narici, Clara Prats, Ian A Macdonald, Paul L Greenhaff.

   BACKGROUND: Bed rest (BR) reduces whole-body insulin-stimulated glucose disposal (GD) and alters muscle fuel metabolism, but little is known about metabolic adaptation from acute to chronic BR nor the mechanisms involved, particularly when volunteers are maintained in energy balance.
METHODS: Healthy males (n = 10, 24.0 ± 1.3 years), maintained in energy balance, underwent 3-day BR (acute BR). A second cohort matched for sex and body mass index (n = 20, 34.2 ± 1.8 years) underwent 56-day BR (chronic BR). A hyperinsulinaemic euglycaemic clamp (60 mU/m2 /min) was performed to determine rates of whole-body insulin-stimulated GD before and after BR (normalized to lean body mass). Indirect calorimetry was performed before and during steady state of each clamp to calculate rates of whole-body fuel oxidation. Muscle biopsies were taken to determine muscle glycogen, metabolite and intramyocellular lipid (IMCL) contents, and the expression of 191 mRNA targets before and after BR. Two-way repeated measures analysis of variance was used to detect differences in endpoint measures.
RESULTS: Acute BR reduced insulin-mediated GD (Pre 11.5 ± 0.7 vs. Post 9.3 ± 0.6 mg/kg/min, P < 0.001), which was unchanged in magnitude following chronic BR (Pre 10.2 ± 0.4 vs. Post 7.9 ± 0.3 mg/kg/min, P < 0.05). This reduction in GD was paralleled by the elimination of the 35% increase in insulin-stimulated muscle glycogen storage following both acute and chronic BR. Acute BR had no impact on insulin-stimulated carbohydrate (CHO; Pre 3.69 ± 0.39 vs. Post 4.34 ± 0.22 mg/kg/min) and lipid (Pre 1.13 ± 0.14 vs. Post 0.59 ± 0.11 mg/kg/min) oxidation, but chronic BR reduced CHO oxidation (Pre 3.34 ± 0.18 vs. Post 2.72 ± 0.13 mg/kg/min, P < 0.05) and blunted the magnitude of insulin-mediated inhibition of lipid oxidation (Pre 0.60 ± 0.07 vs. Post 0.85 ± 0.06 mg/kg/min, P < 0.05). Neither acute nor chronic BR increased muscle IMCL content. Plentiful mRNA abundance changes were detected following acute BR, which waned following chronic BR and reflected changes in fuel oxidation and muscle glycogen storage at this time point.
CONCLUSIONS: Acute BR suppressed insulin-stimulated GD and storage, but the extent of this suppression increased no further in chronic BR. However, insulin-mediated inhibition of fat oxidation after chronic BR was less than acute BR and was accompanied by blunted CHO oxidation. The juxtaposition of these responses shows that the regulation of GD and storage can be dissociated from substrate oxidation. Additionally, the shift in substrate oxidation after chronic BR was not explained by IMCL accumulation but reflected by muscle mRNA and pyruvate dehydrogenase kinase 4 protein abundance changes, pointing to lack of muscle contraction per se as the primary signal for muscle adaptation.

Keywords:  bed rest; fuel oxidation; insulin resistance; muscle metabolism

DOI:  https://doi.org/10.1002/jcsm.13075
Nutrients. 2022 Aug 31. pii: 3600. [Epub ahead of print]14(17):

Vasorin Deletion in C57BL/6J Mice Induces Hepatocyte Autophagy through Glycogen-Mediated mTOR Regulation.

Lichao Yang, Xiaojing Cheng, Wei Shi, Hui Li, Qi Zhang, Shiping Huang, Xuejing Huang, Sha Wen, Ji Gan, Zhouxiang Liao, Junming Sun, Jinning Liang, Yiqiang Ouyang, Min He.

  Abnormal vasorin (Vasn) expression occurs in multiple diseases, particularly liver cancers. Vasn knockout (KO) in mice causes malnutrition, a shortened life span, and decreased physiological functions. However, the causes and underlying mechanisms remain unknown. Here, we established Vasn KO C57BL/6J mice by using the CRISPR/Cas9 system. The animals were weighed, and histology, immunohistochemistry, electronic microscopy, and liver function tests were used to examine any change in the livers. Autophagy markers were detected by Western blotting. MicroRNA (miRNA) sequencing was performed on liver samples and analyses to study the signaling pathway altered by Vasn KO. Significant reductions in mice body and liver weight, accompanied by abnormal liver function, liver injury, and reduced glycogen accumulation in hepatocytes, were observed in the Vasn KO mice. The deficiency of Vasn also significantly increased the number of autophagosomes and the expression of LC3A/B-II/I but decreased SQSTM1/p62 levels in hepatocytes, suggesting aberrant activation of autophagy. Vasn deficiency inhibited glycogen-mediated mammalian target of rapamycin (mTOR) phosphorylation and activated Unc-51-like kinase 1 (ULK1) signaling, suggesting that Vasn deletion upregulates hepatocyte autophagy through the mTOR-ULK1 signaling pathway as a possible cause of diminished life span and health. Our results indicate that Vasn is required for the homeostasis of liver glycogen metabolism upstream of hepatocyte autophagy, suggesting research values for regulating Vasn in pathways related to liver physiology and functions. Overall, this study provides new insight into the role of Vasn in liver functionality.

Keywords:  ULK1; autophagy; glycogen; mTOR; vasorin (Vasn)

DOI:  https://doi.org/10.3390/nu14173600
Pediatr Int. 2022 Jan;64(1): e15286

The earliest enzyme replacement for infantile-onset Pompe disease in Japan.

Vlad Tocan, Yuichi Mushimoto, Kanako Kojima-Ishii, Akane Matsuda, Naoko Toda, Daisuke Toyomura, Yuichiro Hirata, Masafumi Sanefuji, Takaaki Sawada, Yasunari Sakai, Kimitoshi Nakamura, Shouichi Ohga.

   BACKGROUND: Infantile-onset Pompe disease (IOPD) is the most severe phenotype of a lysosomal storage disorder caused by acid alpha-glucosidase (GAA) deficiency. An enzymatic newborn screening (NBS) program started regionally in Japan in 2013 for early enzyme replacement therapy (ERT). We report the ERT responses of the first NBS-identified Japanese IOPD case and of another case diagnosed prior to NBS, to discuss the problems of promptly starting ERT in Japan.
METHODS: Acid alpha-glucosidase activity was measured by fluorometric assay in both patients. The diagnosis of IOPD was confirmed by next-generation followed by Sanger-method sequencing (patient 1) or direct sequencing of polymerase chain reaction (PCR)-amplified products (patient 2) of the GAA gene.
RESULTS: A female infant identified by NBS had a novel out-of-frame (p.F181Dfs*6) variant and a reported pathogenic (p.R600C) variant, along with two pseudodeficiency variants. Enzyme replacement therapy was started at age 58 days when the infant had increased serum levels of creatine kinase and slight myocardial hypertrophy. Clinical and biochemical markers improved promptly. She has been alive and well without delayed development at age 14 months. Patient 2, a Japanese male, received a diagnosis of IOPD at age 5 months before the NBS era. He had a homozygotic variant of GAA (p.R608X), later registered as a cross-reactive immunological material (CRIM)-negative genotype, and developed a high titer of anti-rhGAA antibodies. The patient has survived myocardial hypertrophy with continuous respiratory support for 12 years of ERT.
CONCLUSIONS: Enzyme replacement therapy should not be delayed over the age of 2 months for reversible cardiac function, although CRIM-negative cases may hamper turnaround time reduction.

Keywords:  CRIM status; enzyme replacement therapy; infantile-onset Pompe disease; newborn screening; pseudodeficiency

DOI:  https://doi.org/10.1111/ped.15286