Glycogen metabolism and glycogen storage disorders

Abstract

Glucose is the main energy fuel for the human brain. Maintenance of glucose homeostasis is therefore, crucial to meet cellular energy demands in both-normal physiological states and during stress or increased demands. Glucose is stored as glycogen primarily in the liver and skeletal muscle with a small amount stored in the brain. Liver glycogen primarily maintains blood glucose levels, while skeletal muscle glycogen is utilized during high-intensity exertion, and brain glycogen is an emergency cerebral energy source. Glycogen and glucose transform into one another through glycogen synthesis and degradation pathways. Thus, enzymatic defects along these pathways are associated with altered glucose metabolism and breakdown leading to hypoglycemia ± hepatomegaly and or liver disease in hepatic forms of glycogen storage disorder (GSD) and skeletal ± cardiac myopathy, depending on the site of the enzyme defects. Overall, defects in glycogen metabolism mainly present as GSDs and are a heterogenous group of inborn errors of carbohydrate metabolism. In this article we review the genetics, epidemiology, clinical and metabolic findings of various types of GSD, and glycolysis defects emphasizing current treatment and implications for future directions.

Huddling relieves myocardial glycogen synthesis of Brandt’s voles in mild cold environment

“…Furthermore, Daurian ground squirrels experience an increase in glycogen concentrations in in soleus muscle after two months of low temperature exposure in winter [15]. Excessive glycogen accumulation in the heart can lead to degenerative changes such as arrhythmia, cardiac hypertrophy, and hypotonia [37]. In this study, glycogen content in the myocardium of the CS group was significantly higher than that of the CON group.…”

Is liver glycogen fragility a possible drug target for diabetes?

“…In humans, five phosphoglucomutase isoforms (PGM1-5) have been identified. 45 PGM1 deficiency causes GSD type XIV.…”

“…Subsequently, glucose 6-phosphate is dephosphorylated by glucose-6-phosphatase to free glucose in the endoplasmic reticulum so it can be exported from the cell. 45 Glucose 6-phosphate translocase can transport glucose 6-phosphate from the cytosol to the endoplasmic reticulum.…”

“…45 In this review, we showed that glycogen α particles are molecularly fragile in diabetes patients when compared to healthy individuals: an effect that correlated with the loss of blood-sugar homeostasis in diabetes. 45 In this review, we showed that glycogen α particles are molecularly fragile in diabetes patients when compared to healthy individuals: an effect that correlated with the loss of blood-sugar homeostasis in diabetes.…”

Fasting-Induced Rhabdomyolysis in An Adolescent Girl

“…The last two associations occur most commonly with carnitine palmitoyl transferase II deficiency and the other disorders of lipid metabolism [7,1]. Recognized heritable causes of rhabdomyolysis are defects in the glycogen metabolism and glycolysis, in the respiratory chain or in fatty acid oxidation [5,8]. Within the group of disorders of fatty acid metabolism, carnitine palmitoyl-transferase II deficiency is the most frequently reported condition, but other defects, like VLCAD deficiency, should also been considered [14,6].…”