scholarly journals 1-Deoxysphingolipids, Early Predictors of Type 2 Diabetes, Compromise the Functionality of Skeletal Myoblasts

2021 ◽  
Vol 12 ◽  
Author(s):  
Duyen Tran ◽  
Stephen Myers ◽  
Courtney McGowan ◽  
Darren Henstridge ◽  
Rajaraman Eri ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Muscle Dysfunction ◽  
Dependent Manner

Metabolic dysfunction, dysregulated differentiation, and atrophy of skeletal muscle occur as part of a cluster of abnormalities associated with the development of Type 2 diabetes mellitus (T2DM). Recent interest has turned to the attention of the role of 1-deoxysphingolipids (1-DSL), atypical class of sphingolipids which are found significantly elevated in patients diagnosed with T2DM but also in the asymptomatic population who later develop T2DM. In vitro studies demonstrated that 1-DSL have cytotoxic properties and compromise the secretion of insulin from pancreatic beta cells. However, the role of 1-DSL on the functionality of skeletal muscle cells in the pathophysiology of T2DM still remains unclear. This study aimed to investigate whether 1-DSL are cytotoxic and disrupt the cellular processes of skeletal muscle precursors (myoblasts) and differentiated cells (myotubes) by performing a battery of in vitro assays including cell viability adenosine triphosphate assay, migration assay, myoblast fusion assay, glucose uptake assay, and immunocytochemistry. Our results demonstrated that 1-DSL significantly reduced the viability of myoblasts in a concentration and time-dependent manner, and induced apoptosis as well as cellular necrosis. Importantly, myoblasts were more sensitive to the cytotoxic effects induced by 1-DSL rather than by saturated fatty acids, such as palmitate, which are critical mediators of skeletal muscle dysfunction in T2DM. Additionally, 1-DSL significantly reduced the migration ability of myoblasts and the differentiation process of myoblasts into myotubes. 1-DSL also triggered autophagy in myoblasts and significantly reduced insulin-stimulated glucose uptake in myotubes. These findings demonstrate that 1-DSL directly compromise the functionality of skeletal muscle cells and suggest that increased levels of 1-DSL observed during the development of T2DM are likely to contribute to the pathophysiology of muscle dysfunction detected in this disease.

Loss of HIF-1α impairs GLUT4 translocation and glucose uptake by the skeletal muscle cells

2014 ◽  
Vol 306 (9) ◽  
pp. E1065-E1076 ◽  
Author(s):  
Hidemitsu Sakagami ◽  
Yuichi Makino ◽  
Katsutoshi Mizumoto ◽  
Tsubasa Isoe ◽  
Yasutaka Takeda ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Protein Kinase ◽  
Glucose Metabolism ◽  
Glucose Uptake ◽  
Intracellular Signaling ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Glut4 Translocation

Defects in glucose uptake by the skeletal muscle cause diseases linked to metabolic disturbance such as type 2 diabetes. The molecular mechanism determining glucose disposal in the skeletal muscle in response to cellular stimuli including insulin, however, remains largely unknown. The hypoxia-inducible factor-1α (HIF-1α) is a transcription factor operating in the cellular adaptive response to hypoxic conditions. Recent studies have uncovered pleiotropic actions of HIF-1α in the homeostatic response to various cellular stimuli, including insulin under normoxic conditions. Thus we hypothesized HIF-1α is involved in the regulation of glucose metabolism stimulated by insulin in the skeletal muscle. To this end, we generated C2C12myocytes in which HIF-1α is knocked down by short-hairpin RNA and examined the intracellular signaling cascade and glucose uptake subsequent to insulin stimulation. Knockdown of HIF-1α expression in the skeletal muscle cells resulted in abrogation of insulin-stimulated glucose uptake associated with impaired mobilization of glucose transporter 4 (GLUT4) to the plasma membrane. Such defect seemed to be caused by reduced phosphorylation of the protein kinase B substrate of 160 kDa (AS160). AS160 phosphorylation and GLUT4 translocation by AMP-activated protein kinase activation were abrogated as well. In addition, expression of the constitutively active mutant of HIF-1α (CA-HIF-1α) or upregulation of endogenous HIF-1α in C2C12cells shows AS160 phosphorylation comparable to the insulin-stimulated level even in the absence of insulin. Accordingly GLUT4 translocation was increased in the cells expressing CA-HIF1α. Taken together, HIF-1α is a determinant for GLUT4-mediated glucose uptake in the skeletal muscle cells thus as a possible target to alleviate impaired glucose metabolism in, e.g., type 2 diabetes.

scholarly journals In vitro anti-diabetic assessment of guavanoic acid functionalized gold nanoparticles in regulating glucose transport using L6 rat skeletal muscle cells

2020 ◽  
Vol 11 (7) ◽  
pp. 814-822
Author(s):  
K. Govindaraju ◽  
K. S. Uma Suganya
Keyword(s):  
Skeletal Muscle ◽  
Gold Nanoparticles ◽  
Glucose Uptake ◽  
Glucose Transport ◽  
Muscle Cells ◽  
Pi3k Inhibitor ◽  
Skeletal Muscle Cells ◽  
Rat Skeletal Muscle ◽  
Functionalized Gold Nanoparticles

Glucose uptake patterns of guavanoic acid and guavanoic acid functionalized gold nanoparticles in the presence of genistein (IRTK inhibitor) and wortmannin (PI3K inhibitor).

scholarly journals The exocyst complex regulates insulin-stimulated glucose uptake of skeletal muscle cells

2019 ◽  
Vol 317 (6) ◽  
pp. E957-E972
Author(s):  
Brent A. Fujimoto ◽  
Madison Young ◽  
Lamar Carter ◽  
Alina P. S. Pang ◽  
Michael J. Corley ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Plasma Membrane ◽  
Cell Surface ◽  
Glucose Uptake ◽  
Glucose Transporter ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Cell Surface Receptor ◽  
Exocyst Complex

Skeletal muscle handles ~80–90% of the insulin-induced glucose uptake. In skeletal muscle, insulin binding to its cell surface receptor triggers redistribution of intracellular glucose transporter GLUT4 protein to the cell surface, enabling facilitated glucose uptake. In adipocytes, the eight-protein exocyst complex is an indispensable constituent in insulin-induced glucose uptake, as it is responsible for the targeted trafficking and plasma membrane-delivery of GLUT4. However, the role of the exocyst in skeletal muscle glucose uptake has never been investigated. Here we demonstrate that the exocyst is a necessary factor in insulin-induced glucose uptake in skeletal muscle cells as well. The exocyst complex colocalizes with GLUT4 storage vesicles in L6-GLUT4myc myoblasts at a basal state and associates with these vesicles during their translocation to the plasma membrane after insulin signaling. Moreover, we show that the exocyst inhibitor endosidin-2 and a heterozygous knockout of Exoc5 in skeletal myoblast cells both lead to impaired GLUT4 trafficking to the plasma membrane and hinder glucose uptake in response to an insulin stimulus. Our research is the first to establish that the exocyst complex regulates insulin-induced GLUT4 exocytosis and glucose metabolism in muscle cells. A deeper knowledge of the role of the exocyst complex in skeletal muscle tissue may help our understanding of insulin resistance in type 2 diabetes.

scholarly journals AN IN VITRO STUDY OF SYZYGIUM CUMINI SEED EXTRACT ON GLUCOSE UPTAKE ACTIVITY IN L-6 CELL LINES

2019 ◽  
Vol 9 (4-A) ◽  
pp. 256-259
Author(s):  
Maneemegalai Sivaprakasam ◽  
Narmatha M
Keyword(s):  
Diabetes Mellitus ◽  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Ethanol Extract ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Syzygium Cumini ◽  
Rat Skeletal Muscle ◽  
Uptake Activity

Diabetes mellitus is the most common endocrine disorder. The plant Syzygium cumini has been used in traditional medicine for the treatment of diabetes. The present study investigated the effect of ethanol extract of S. cumini seeds on uptake of glucose by L-6 rat skeletal muscle cells. S. cumini seeds were extracted with varying solvents and quantitative phytochemical analysis was carried out, ethanol extract of seeds exhibited higher content of tested phytochemicals. The effect of different concentrations (300µg/ml – 1000µg/ml) of ethanol extract of seeds were studied on glucose uptake activity of L-6 rat skeletal muscle cells. It was observed that with the increase in concentration, the glucose uptake activity was also increased. The results of the study supports and demonstrates the antidiabetic potential of ethanol seed extracts of Syzygium cumini utilizing in vitro model. KEY WORDS: Diabetes mellitus, Syzygium cumini, phytochemicals, glucose uptake, L-6 cells

Genetic downregulation of AMPK-α isoforms uncovers the mechanism by which metformin decreases FA uptake and oxidation in skeletal muscle cells

2010 ◽  
Vol 299 (6) ◽  
pp. C1549-C1561 ◽  
Author(s):  
Lindsey D. Bogachus ◽  
Lorraine P. Turcotte
Keyword(s):  
Skeletal Muscle ◽  
Glucose Uptake ◽  
Muscle Metabolism ◽  
Muscle Cells ◽  
Time Dependent ◽  
Skeletal Muscle Cells ◽  
Dependent Manner ◽  
Ampk Activity ◽  
Palmitate Uptake ◽  
Amp Activated Protein Kinase

Metformin is known to improve insulin sensitivity in part via a rise in AMP-activated protein kinase (AMPK) activity and alterations in muscle metabolism. However, a full understanding of how metformin alters AMPK-α1 vs. AMPK-α2 activation remains unknown. To study this question, L6 skeletal muscle cells were treated with or without RNAi oligonucleotide sequences to downregulate AMPK-α1 or AMPK-α2 protein expression and incubated with or without 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) or metformin and/or insulin. In contrast to AICAR, which preferentially activated AMPK-α2, metformin preferentially activated AMPK-α1 in a dose- and time-dependent manner. Metformin increased ( P < 0.05) glucose uptake and plasma membrane (PM) Glut4 in a dose- and time-dependent manner. Metformin significantly reduced palmitate uptake ( P < 0.05) and oxidation ( P < 0.05), and this was accompanied by a similar decrease ( P < 0.05) in PM CD36 content but with no change in acetyl-CoA carboxylase (ACC) phosphorylation ( P > 0.05). AICAR and metformin similarly increased ( P < 0.05) nuclear silent mating-type information regulator 2 homolog 1 (SIRT1) activity. Downregulation of AMPK-α1 completely prevented the metformin-induced reduction in palmitate uptake and oxidation but only partially reduced the metformin-induced increase in glucose uptake. Downregulation of AMPK-α2 had no effect on metformin-induced glucose uptake, palmitate uptake, and oxidation. The increase in SIRT1 activity induced by metformin was not affected by downregulation of either AMPK-α1 or AMPK-α2. Our data indicate that, in muscle cells, the inhibitory effects of metformin on fatty acid metabolism occur via preferential phosphorylation of AMPK-α1, and the data indicate that cross talk between AMPK and SIRT1 does not favor either AMPK isozyme.

Thiazolidinediones upregulate impaired fatty acid uptake in skeletal muscle of type 2 diabetic subjects

2003 ◽  
Vol 285 (2) ◽  
pp. E354-E362 ◽  
Author(s):  
Hubertina M. Wilmsen ◽  
Theodore P. Ciaraldi ◽  
Leslie Carter ◽  
Nabeela Reehman ◽  
Sunder R. Mudaliar ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Skeletal Muscle ◽  
Fatty Acid ◽  
Muscle Cells ◽  
Skeletal Muscle Cells ◽  
Acid Uptake ◽  
Cd36 Expression ◽  
Palmitate Uptake ◽  
Type 2 Diabetic

We examined the regulation of free fatty acid (FFA, palmitate) uptake into skeletal muscle cells of nondiabetic and type 2 diabetic subjects. Palmitate uptake included a protein-mediated component that was inhibited by phloretin. The protein-mediated component of uptake in muscle cells from type 2 diabetic subjects (78 ± 13 nmol · mg protein-1 · min-1) was reduced compared with that in nondiabetic muscle (150 ± 17, P < 0.01). Acute insulin exposure caused a modest (16 ± 5%, P < 0.025) but significant increase in protein-mediated uptake in nondiabetic muscle. There was no significant insulin effect in diabetic muscle (+19 ± 19%, P = not significant). Chronic (4 day) treatment with a series of thiazolidinediones, troglitazone (Tgz), rosiglitazone (Rgz), and pioglitazone (Pio) increased FFA uptake. Only the phloretin-inhibitable component was increased by treatment, which normalized this activity in diabetic muscle cells. Under the same conditions, FFA oxidation was also increased by thiazolidinedione treatment. Increases in FFA uptake and oxidation were associated with upregulation of fatty acid translocase (FAT/CD36) expression. FAT/CD36 protein was increased by Tgz (90 ± 22% over control), Rgz (146 ± 42%), and Pio (111 ± 37%, P < 0.05 for all 3) treatment. Tgz treatment had no effect on fatty acid transporter protein-1 and membrane-associated plasmalemmal fatty acid-binding protein mRNA expression. We conclude that FFA uptake into cultured muscle cells is, in part, protein mediated and acutely insulin responsive. The basal activity of FFA uptake is impaired in type 2 diabetes. In addition, chronic thiazolidinedione treatment increased FFA uptake and oxidation into cultured human skeletal muscle cells in concert with upregulation of FAT/CD36 expression. Increased FFA uptake and oxidation may contribute to lower circulating FFA levels and reduced insulin resistance in skeletal muscle of individuals with type 2 diabetes following thiazolidinedione treatment.

scholarly journals Resistin and Type 2 Diabetes: Regulation of Resistin Expression by Insulin and Rosiglitazone and the Effects of Recombinant Resistin on Lipid and Glucose Metabolism in Human Differentiated Adipocytes

2003 ◽  
Vol 88 (12) ◽  
pp. 6098-6106 ◽  
Author(s):  
Philip G. McTernan ◽  
FFolliott M. Fisher ◽  
George Valsamakis ◽  
Rajkumar Chetty ◽  
Alison Harte ◽  
...  
Keyword(s):  
Type 2 Diabetes ◽  
Glucose Uptake ◽  
Protein Secretion ◽  
In Vitro Studies ◽  
Dependent Manner ◽  
Diabetes Status ◽  
Human Diabetes ◽  
Type 2 Diabetic

Abstract Resistin, an adipocyte secreted factor, has been suggested to link obesity with type 2 diabetes in rodent models, but its relevance to human diabetes remains uncertain. Although previous studies have suggested a role for this adipocytokine as a pathogenic factor, its functional effects, regulation by insulin, and alteration of serum resistin concentration by diabetes status remain to be elucidated. Therefore, the aims of this study were to analyze serum resistin concentrations in type 2 diabetic subjects; to determine the in vitro effects of insulin and rosiglitazone (RSG) on the regulation of resistin, and to examine the functional effects of recombinant human resistin on glucose and lipid metabolism in vitro. Serum concentrations of resistin were analyzed in 45 type 2 diabetic subjects and 34 nondiabetic subjects. Subcutaneous human adipocytes were incubated in vitro with insulin, RSG, and insulin in combination with RSG to examine effects on resistin secretion. Serum resistin was increased by approximately 20% in type 2 diabetic subjects compared with nondiabetic subjects (P = 0.004) correlating with C-reactive protein. No other parameters, including adiposity and fasting insulin levels, correlated with serum resistin in this cohort. However, in vitro, insulin stimulated resistin protein secretion in a concentration-dependent manner in adipocytes [control, 1215 ± 87 pg/ml (mean ± sem); 1 nm insulin, 1414.0 ± 89 pg/ml; 1 μm insulin, 1797 ± 107 pg/ml (P &lt; 0.001)]. RSG (10 nm) reduced the insulin-mediated rise in resistin protein secretion (1 nm insulin plus RSG, 971 ± 35 pg/ml; insulin, 1 μm insulin plus RSG, 1019 ± 28 pg/ml; P &lt; 0.01 vs. insulin alone). Glucose uptake was reduced after treatment with 10 ng/ml recombinant resistin and higher concentrations (P &lt; 0.05). Our in vitro studies demonstrated a small, but significant, reduction in glucose uptake with human recombinant resistin in differentiated preadipocytes. In human abdominal sc adipocytes, RSG blocks the insulin-mediated release of resistin secretion in vitro. In conclusion, elevated serum resistin in human diabetes reflects the subclinical inflammation prevalent in type 2 diabetes. Our in vitro studies suggest a modest effect of resistin in reducing glucose uptake, and suppression of resistin expression may contribute to the insulin-sensitizing and glucose-lowering actions of the thiazolidinediones.

Role of laminin and fibronectin in selecting myogenic versus fibrogenic cells from skeletal muscle cells in vitro

1986 ◽  
Vol 117 (2) ◽  
pp. 628-635 ◽  
Author(s):  
Uwe Kühl ◽  
Mücella Öcalan ◽  
Rupert Timpl ◽  
Klaus von der Mark
Keyword(s):  
Skeletal Muscle ◽  
Muscle Cells ◽  
Skeletal Muscle Cells
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