Glycogen—Endoplasmic Reticulum Connection in the Liver

Abstract

Glycogen, the branched polymer of glucose is found mainly in the liver and muscle in mammals. Along with several other proteins, glycogen forms separate cellular organelles, and particles in cells. Glycogen particles in the liver have a special metabolic and also regulatory connection to the intracellular endomembrane system, particularly the endoplasmic reticulum. This connection is part of the organelle homeostasis in hepatocytes and forms a “glycogenoreticular system”. The actual size of hepatic glycogen stores and the rate of glycogenolysis determines several essential liver-specific metabolic processes, such as glucose secretion for the maintenance of blood glucose levels or the glucuronidation of certain vital endo-, and xenobiotics, and are also related to liver antioxidant defense. In starvation, and in certain physiological and pathological states, where glycogen stores are depleted, functions of the glycogenoreticular system are altered. The starvation-induced depletion of hepatic glycogen content changes the biotransformation of various endo- and xenobiotics. This can be observed especially in acute DILI (drug-induced liver injury) due to paracetamol overdose, which is the most common cause of acute liver failure in the West.

Amphibian pore-forming protein βγ-CAT drives extracellular nutrient scavenging under cell nutrient deficiency

“…Considering the pivotal role of glucose and considering glycogen as another important source of glucose, 27 , 28 we also assayed the content of glycogen in isolated hepatocytes ( Figure S1 D). Indeed, the glycogen content of isolated toad hepatocytes gradually decreased during in vitro culture in both Glc + /Gln + /Pyr + and Glc ˉ /Gln ˉ /Pyr ˉ conditions, and decreased to a low level after 5 h’ culture.…”

Effects of maternal advanced lipoxidation end products diet on the glycolipid metabolism and gut microbiota in offspring mice

“…Insulin and leptin were reliable biomarker of glycolipid metabolism disorders ( 26 ). Furthermore, glycogen is the main intracellular storage form of glucose in the liver, and glycogen levels are thought to be associated with insulin resistance in mice ( 27 ). The AB-PAS staining in the liver further confirmed the effect of HALEs diet on the hepatic glycogen content of offspring.…”

TEAD1, MYO7A and NDUFC2 are novel functional genes associated with glucose metabolism in BXD recombinant inbred population

“…8,9 As the starvation time is prolonged and glycogen stores have been exhausted, gluconeogenesis, that is, de novo glucose synthesis from available precursors, becomes the alternative way to maintain blood glucose levels. 10,11 Over the past two decades, various research approaches, including linkage analyses, candidate gene investigations, and large-scale genome-wide association studies (GWAS), have successfully identified numerous genetic variants, genomic regions, and susceptibility genes associated with disorders in glucose metabolism. 12,13 For example, 568 genetic loci, including 318 novel loci, for diabetes were identified in 1 178 873 samples from Biobank Japan and other studies.…”

“…During short‐term fasting periods, glycogenolysis is mainly motivated in the liver; hepatocyte‐stored glycogen breaks down into glucose and is released into the blood 8,9 . As the starvation time is prolonged and glycogen stores have been exhausted, gluconeogenesis, that is, de novo glucose synthesis from available precursors, becomes the alternative way to maintain blood glucose levels 10,11 . Over the past two decades, various research approaches, including linkage analyses, candidate gene investigations, and large‐scale genome‐wide association studies (GWAS), have successfully identified numerous genetic variants, genomic regions, and susceptibility genes associated with disorders in glucose metabolism 12,13 .…”