SIMVASTATIN REDUCES INSULIN-LIKE GROWTH FACTOR-1 SIGNALING IN DIFFERENTIATING C2C12 MOUSE MYOBLAST CELLS IN AN HMG-CoA REDUCTASE INHIBITION-INDEPENDENT MANNER

Abstract

-Inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG-CoA) reductase occasionally cause myopathy characterized by weakness, pain, and elevated serum creatine phosphokinase (CK). In this study, we investigated the effects of simvastatin, an HMG-CoA reductase inhibitor, on the viability and insulin-like growth factor-1 (IGF-1) signaling in differentiating C2C12 mouse myoblast cells. Simvastatin decreased cell viability and CK activity, a marker of myogenesis, in differentiating cells in a dosedependent manner. Although the simvastatin-induced decrease in viability in proliferating and differentiated cells was completely abolished by mevalonate or geranylgeranyl-pyrophosphate, the inhibitory effects of simvastatin in differentiating cells were not abolished by mevalonate or isoprenoid derivatives of mevalonate. Moreover, the sensitivity of differentiating cells to simvastatin regarding cell viability was about 7 times higher than that of proliferating cells. After induction of differentiation in the presence of 1 μM simvastatin for 2 days, IGF-1-induced activation of ERK1/2 and Akt was significantly decreased. Although mRNA expression of the IGF-1 receptor β-chain (IGF-1Rβ) did not change, protein level of the 200 kDa IGF-1Rβ precursor was significantly increased by simvastatin in a dose-dependent manner. Mevalonate did not abolish the effect of simvastatin on IGF-1Rβ expression. These results suggest that simvastatin decreases IGF-1 signaling via a regulation of the post-translational modification of IGF-1Rβ in an HMG-CoA reductase inhibition-independent manner.

Simvastatin represses protein synthesis in the muscle-derived C2C12cell line with a concomitant reduction in eukaryotic initiation factor 2B expression

“…It is also important to consider that some of the effects of statins occur in an HMG-CoA reductase inhibition-independent manner. For example, IGF-I signaling is impaired in differentiating C 2 C 12 myoblasts treated with simvastatin, but the effects are not rescued by addition of mevalonate (the product of HMG-CoA reductase) or its isoprenoid derivatives (27). However, in the present investigation, the simvastatin-induced repression of protein synthesis and eIF2B⑀ protein expression were both completely prevented by the addition of mevalonate, implicating the product of HMG-CoA reductase as a mediator of these effects.…”

“…One important regulator in common to both the protein synthesis and degradation pathways is the AGC serine-threonine kinase Akt. Decreased phosphorylation of Akt has been reported in response to statin treatment in the mouse C 2 C 12 myoblast cell line (11,27) as well as in rat skeletal muscle in vivo (21). One downstream consequence of reduced Akt activity in response to statins is increased expression of the E3 ligases MAFbx and MuRF1 that are associated with muscle protein degradation (11,21).…”

Growth Hormone Secretagogues Exert Differential Effects on Skeletal Muscle Calcium Homeostasis in Male Rats Depending on the Peptidyl/Nonpeptidyl Structure

“…Reportedly, C2C12 cells express the GHS-R1a (37,38). Cell viability was assessed using the colorimetric [2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2H-tetrazolium monosodium salt (WST-8) assay (cell counting kit, CCK8, Vinci-Biochem) (39,40). Cells were seeded in 96-well cultures at a density of ϳ 1 ϫ 10 4 cells per well and cultured for 18 h to allow for attachment.…”

Potential role of nonstatin cholesterol lowering agents

“…Statins, cholesterol-lowering drugs, represent the most frequently prescribed medications in industrialized countries where coronary diseases, consistent with hypercholesterolemia, represent the principal cause of death (2). These drugs inhibit 3b-hydroxy-3b-methylglutaryl coenzyme A reductase (HMGR), the key enzyme of the cholesterol biosynthetic pathway that is involved also in the biosynthesis of fundamental compounds for cell physiology such as ubiquinone, dolichol, and prenyls (3).…”