scholarly journals Effects of Retinoic Acid and Insulin on Glycogen Content and Expression Levels of Glycogenic Proteins in Differentiating L6 Myocytes

2020 ◽  
Vol 4 (Supplement_2) ◽  
pp. 97-97
Author(s):  
Aaron Armstrong
Keyword(s):  
Retinoic Acid ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Control Group ◽  
Expression Levels ◽  
Insulin Group ◽  
Total P ◽  
L6 Myocytes

Abstract Objectives The skeletal muscle is critical for the control of glucose homeostasis partially through glycogenesis. The effects of retinoic acid (RA) on glycogen content and expressions of key glycogenic proteins without or with insulin in L6 rat myocytes deserve to be studied. Methods L6 myocytes at confluence were induced to differentiation using DMEM with 2% horse serum. Cells were incubated in medium with vehicle control or 1 μM RA without or with 10 nM insulin for 2, 4, and 6 days. Glycogen was extracted and analyzed using α-amyloglucosidase and released glucose assay. Proteins in cell lysates from parallel groups were extracted and subjected to analysis using western blotting. The expression levels of glycogen synthase (GS), phospho-glycogen synthase (Ser 641) (p-GS), glycogen synthase kinase 3-β(GSK3β), and phospho-glycogen synthase kinase 3-β (p-GSK3β) were determined using their specific antibodies, and then quantified with ImageJ software. Results The RA + insulin group had higher glycogen content than the control group on days 2 to 6. A synergistic effect of RA and insulin were observed on day 2. GS expression was synergistically induced in the RA + insulin group on each day. The total p-GS normalized to β-actin in the RA + insulin group was higher than that in the control on day 2. However, the ratio of p-GS/GS in the RA + insulin group was lower than that in the control on day 2 and in RA group on day 6, respectively. GSK3β expression levels in insulin and RA + insulin groups were higher than that in the control on day two. The total p-GSK3β normalized to β-actin showed an increase in the insulin group compared to the RA group on day 6. The p-GSK3β/GSK3β ratio in the insulin group was higher than that in RA and RA + insulin groups on day 6. Conclusions Treatments with RA and insulin increase the glycogen content in L6 cells via upregulation of glycogenesis. A synergy of RA and insulin can be seen. The increases of total GS and decreases of p-GS/GS ratio contribute to the elevation of GS activity. RA likely exerts its glycogenic effects through changes of the total GS level and phosphorylation by GSK3β. Funding Sources Internal fund at the Univenrsity of Tennessee.

scholarly journals Ursolic acid and luteolin-7-glucoside improve lipid profiles and increase liver glycogen content through glycogen synthase kinase-3

2010 ◽  
Vol 24 (S2) ◽  
pp. S220-S224 ◽  
Author(s):  
Marisa F. Azevedo ◽  
Çagri Camsari ◽  
Carla M. Sá ◽  
Cristovao F. Lima ◽  
Manuel Fernandes-Ferreira ◽  
...  
Keyword(s):  
Ursolic Acid ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Liver Glycogen ◽  
Lipid Profiles ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Liver Glycogen Content

scholarly journals Exercise training attenuated the PKB and GSK-3 dephosphorylation in the myocardium of ZDF rats

2004 ◽  
Vol 96 (5) ◽  
pp. 1606-1612 ◽  
Author(s):  
Claude Lajoie ◽  
Angelino Calderone ◽  
François Trudeau ◽  
Nathalie Lavoie ◽  
Guy Massicotte ◽  
...  
Keyword(s):  
Protein Kinase ◽  
Exercise Training ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Protein Kinase B ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Zucker Diabetic Fatty Rat ◽  
Glucose Levels ◽  
Zucker Diabetic Fatty Rats

Cardiac dysfunction is a severe secondary effect of Type 2 diabetes. Recruitment of the protein kinase B/glycogen synthase kinase-3 pathway represents an integral event in glucose homeostasis, albeit its regulation in the diabetic heart remains undefined. Thus the following study tested the hypothesis that the regulation of protein kinase B/glycogen synthase kinase-3 was altered in the myocardium of the Zucker diabetic fatty rat. Second, exercise has been shown to improve glucose homeostasis, and, in this regard, the effect of swimming training on the regulation of protein kinase B/glycogen synthase kinase-3 in the diabetic rat heart was examined. In the sedentary Zucker diabetic fatty rats, glucose levels were elevated, and cardiac glycogen content increased, compared with wild type. A 13-wk swimming regimen significantly reduced plasma glucose levels and cardiac glycogen content and partially normalized protein kinase B-serine473, protein kinase B-threonine308, and glycogen synthase kinase-3α phosphorylation in Zucker diabetic fatty rats. In conclusion, hyperglycemia and increased cardiac glycogen content in the Zucker diabetic fatty rats were associated with dysregulation of protein kinase B/glycogen synthase kinase-3 phosphorylation. These anomalies in the Zucker diabetic fatty rat were partially normalized with swimming. These data support the premise that exercise training may protect the heart against the deleterious consequences of diabetes.

scholarly journals Inhibition of Insulin-Stimulated Glycogen Synthesis by 5-Aminoimidasole-4-Carboxamide-1-β-d-Ribofuranoside-Induced Adenosine 5′-Monophosphate-Activated Protein Kinase Activation: Interactions with Akt, Glycogen Synthase Kinase 3-3α/β, and Glycogen Synthase in Isolated Rat Soleus Muscle

Endocrinology ◽  
2006 ◽  
Vol 147 (11) ◽  
pp. 5170-5177 ◽  
Author(s):  
S. Fediuc ◽  
M. P. Gaidhu ◽  
R. B. Ceddia
Keyword(s):  
Protein Kinase ◽  
Glycogen Content ◽  
Glycogen Synthase ◽  
Glycogen Synthesis ◽  
Lactate Production ◽  
Glycogen Synthase Kinase ◽  
Glycogen Synthase Kinase 3 ◽  
Kinase Activation ◽  
Protein Kinase Activation ◽  
Amp Activated Protein Kinase

The aim of this study was to investigate the effects of 5-aminoimidasole-4-carboxamide-1-β-d-ribofuranoside (AICAR)-induced AMP-activated protein kinase activation on glycogen metabolism in soleus (slow twitch, oxidative) and epitrochlearis (fast twitch, glycolytic) skeletal muscles. Isolated soleus and epitrochlearis muscles were incubated in the absence or presence of insulin (100 nm), AICAR (2 mm), and AICAR plus insulin. In soleus muscles exposed to insulin, glycogen synthesis and glycogen content increased 6.4- and 1.3-fold, respectively. AICAR treatment significantly suppressed (∼60%) insulin-stimulated glycogen synthesis and completely prevented the increase in glycogen content induced by insulin. AICAR did not affect either basal or insulin-stimulated glucose uptake but significantly increased insulin-stimulated (∼20%) lactate production in soleus muscles. Interestingly, basal glucose uptake was significantly increased (∼1.4-fold) in the epitrochlearis muscle, even though neither basal nor insulin-stimulated rates of glycogen synthesis, glycogen content, and lactate production were affected by AICAR. We also report the novel evidence that AICAR markedly reduced insulin-induced Akt-Thr308 phosphorylation after 15 and 30 min exposure to insulin, which coincided with a marked reduction in glycogen synthase kinase 3 (GSK)-3α/β phosphorylation. Importantly, phosphorylation of glycogen synthase was increased by AICAR treatment 45 min after insulin stimulation. Our results indicate that AICAR-induced AMP-activated protein kinase activation caused a time-dependent reduction in Akt308 phosphorylation, activation of glycogen synthase kinase-3α/β, and the inactivation of glycogen synthase, which are compatible with the acute reduction in insulin-stimulated glycogen synthesis in oxidative but not glycolytic skeletal muscles.

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