High glucose‐mediated alterations of mechanisms important in myogenesis of mouse C2C12 myoblasts

Abstract

We have examined the progression and regulation of myogenesis, cellular levels of IGFBP-4, -5, -6, and several extracellular matrix (ECM) proteins (fibronectin, integrin α5, β1 subunits and a disintegrin metalloprotease ADAM12) in murine C2C12 myoblasts during 3-day differentiation under high glucose alone or combined with high insulin, factors characteristic for type 1 and 2 diabetes. High ambient glucose inhibited myogenesis of C2C12 myoblasts, an effect manifested by a twofold decrease in myoblast fusion, a drop in intracellular MyoD, myogenin and MHC levels, and increased cellular content of active myostatin isoform. Reduction in myogenesis by high glucose is accompanied by increase in cellular levels of IGFBP-4 and -6 and decrease in IGFBP-5. High glucose could modify ECM components assembly, by the increase in fibronectin levels and the decrease in metalloprotease ADAM12, without the effect on integrin α5 and β1 subunits. In contrast, high glucose and high insulin activate myoblast differentiation, manifested by an increase in fusion index and myogenin, as well as a drop in myostatin levels. The presence of high insulin prevented high-glucose-dependent changes in IGFBPs and ECM proteins. The data indicate the potential mechanisms of the influence of extracellular environment associated with maternal diabetes and insulin resistance on foetal myogenesis.

Myostatin Induces Insulin Resistance via Casitas B-Lineage Lymphoma b (Cblb)-mediated Degradation of Insulin Receptor Substrate 1 (IRS1) Protein in Response to High Calorie Diet Intake

“…Indeed we observed that in vitro treatment of C2C12 and HepG2 cells with high glucose or fatty acid (palmitate) as well as subjecting mice to high glucose or HFD feeding in vivo significantly increased Mstn levels, suggesting that Mstn expression is indeed under the control of major nutrient factors like glucose and fatty acids. In agreement with this, high glucose treatment of C2C12 has been previously shown to increase Mstn, block myogenesis, and promote myotube atrophy (10). Specifically, our results revealed that glucose and fatty acid/HFD treatment induce Mstn via independent transcription factors; although SREBP1c was shown to be sufficient to induce Mstn in response to fatty acids by binding to an E-box motif, ChREBP was found to be responsible for glucosemediated induction of Mstn through interaction with a ChoRE.…”

“…Moreover, peroxisome proliferator-activated receptor-␥, CCAAT/enhancer-binding protein-␣, and sterol regulatory element-binding protein 1c (SREBP1c) have been shown to increase Mstn promoter activity in 3T3L1 adipocytes (4). Furthermore nutrients like high protein diet or high glucose treatment have been reported to increase Mstn expression (10,11). However, the mechanism(s) behind up-regulation of Mstn in response to high nutrients and, for that matter, the downstream targets of Mstn that promote the development of insulin resistance remain poorly focused.…”

The Effect of High Glucose on Mechanisms Controlling Proliferation of Mouse C2C12 Myoblasts

“…In the previous study we supported the hypothesis that expression of key myogenic regulatory factors, IGF binding proteins and important extracellular matrix components could be targeted by high glucose in differentiating myocytes [13]. Present results indicate the subsequent mechanism of the modulatory effect of high extracellular glucose on skeletal muscle growth.…”

“…Our recent observations revealed some modifications of myogenic differentiation under high glucose treatment, manifested by decreased fusion index, myogenin and myosin heavy chain expression as well as an increased level of myostatin [13]. The purpose of the present study was to examine the mechanisms controlling myoblast proliferation, i.e.…”

“…The final concentration of glucose in the incubation medium amounted to 15 mmol/l and in our early studies six-day differentiation of C2C12 myoblasts under this condition resulted in insulin and IGF-I resistance manifested by the impairment of protein synthesis and protein kinases phosphorylation [14,15]. According to our recent study this concentration of glucose was effective in inhibiting of myogenesis of C2C12 myoblasts, manifested by decreased fusion index and the expression of myogenic regulatory factors: MyoD, myogenin and myosin heavy chain [13].…”