Muscle-specific overexpression of IGF-I improves E-C coupling in skeletal muscle fibers from dystrophic mdx mice

2008 ◽  
Vol 294 (1) ◽  
pp. C161-C168 ◽  
Author(s):  
Jonathan D. Schertzer ◽  
Chris van der Poel ◽  
Thea Shavlakadze ◽  
Miranda D. Grounds ◽  
Gordon S. Lynch
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Muscle Fibers ◽  
Transcript Level ◽  
Direct Result ◽  
Mdx Mice ◽  
Contractile Apparatus ◽  
Dystrophic Muscle ◽  
Insulin Growth Factor ◽  
Igf I

Duchenne muscular dystrophy (DMD) is a lethal X-linked disease caused by the absence of functional dystrophin. Abnormal excitation-contraction (E-C) coupling has been reported in dystrophic muscle fibers from mdx mice, and alterations in E-C coupling components may occur as a direct result of dystrophin deficiency. We hypothesized that muscle-specific overexpression of insulin-growth factor-1 (IGF-I) would reduce E-C coupling failure in mdx muscle. Mechanically skinned extensor digitorum longus muscle fibers from mdx mice displayed a faster decline in depolarization-induced force responses (DIFR); however, there were no differences in sarcoplasmic reticulum (SR)-mediated Ca2+ resequestration or in the properties of the contractile apparatus when compared with nondystrophic controls. The rate of DIFR decline was restored to control levels in fibers from transgenic mdx mice that overexpressed IGF-I in skeletal muscle ( mdx/IGF-I mice). Dystrophic muscles have a lower transcript level of a specific dihydropyridine receptor (DHPR) isoform, and IGF-I-mediated changes in E-C coupling were associated with increased transcript levels of specific DHPR isoforms involved in Ca2+ regulation. Importantly, IGF-I overexpression also increased the sensitivity of the contractile apparatus to Ca2+. The results demonstrate that IGF-I can ameliorate fundamental aspects of E-C coupling failure in dystrophic muscle fibers and that these effects are important for the improvements in cellular function induced by this growth factor.

scholarly journals Extensive but Coordinated Reorganization of the Membrane Skeleton in Myofibers of Dystrophic (mdx) Mice

1999 ◽  
Vol 144 (6) ◽  
pp. 1259-1270 ◽  
Author(s):  
McRae W. Williams ◽  
Robert J. Bloch
Keyword(s):  
Skeletal Muscle ◽  
Membrane Proteins ◽  
Muscle Fibers ◽  
Membrane Skeleton ◽  
Confocal Imaging ◽  
Mdx Mouse ◽  
Mdx Mice ◽  
Intracellular Membrane ◽  
Dystrophic Muscle ◽  
Dihydropyridine Receptors

We used immunofluorescence techniques and confocal imaging to study the organization of the membrane skeleton of skeletal muscle fibers of mdx mice, which lack dystrophin. β-Spectrin is normally found at the sarcolemma in costameres, a rectilinear array of longitudinal strands and elements overlying Z and M lines. However, in the skeletal muscle of mdx mice, β-spectrin tends to be absent from the sarcolemma over M lines and the longitudinal strands may be disrupted or missing. Other proteins of the membrane and associated cytoskeleton, including syntrophin, β-dystroglycan, vinculin, and Na,K-ATPase are also concentrated in costameres, in control myofibers, and mdx muscle. They also distribute into the same altered sarcolemmal arrays that contain β-spectrin. Utrophin, which is expressed in mdx muscle, also codistributes with β-spectrin at the mutant sarcolemma. By contrast, the distribution of structural and intracellular membrane proteins, including α-actinin, the Ca-ATPase and dihydropyridine receptors, is not affected, even at sites close to the sarcolemma. Our results suggest that in myofibers of the mdx mouse, the membrane- associated cytoskeleton, but not the nearby myoplasm, undergoes widespread coordinated changes in organization. These changes may contribute to the fragility of the sarcolemma of dystrophic muscle.

scholarly journals IGF‐I improves excitation‐contraction coupling in skeletal muscle fibers of dystrophic mdx mice

2007 ◽  
Vol 21 (6) ◽  
Author(s):  
Chris van der Poel ◽  
Jonathan D Schertzer ◽  
Thea Shavlakadze ◽  
Miranda D Grounds ◽  
Gordon S Lynch
Keyword(s):  
Skeletal Muscle ◽  
Muscle Fibers ◽  
Mdx Mice ◽  
Excitation Contraction Coupling ◽  
Contraction Coupling ◽  
Skeletal Muscle Fibers ◽  
Igf I

Branched fibers in dystrophic mdx muscle are associated with a loss of force following lengthening contractions

2007 ◽  
Vol 293 (3) ◽  
pp. C985-C992 ◽  
Author(s):  
S. Chan ◽  
S. I. Head ◽  
J. W. Morley
Keyword(s):  
Skeletal Muscle ◽  
Muscular Dystrophy ◽  
Extensor Digitorum Longus ◽  
Muscle Fibers ◽  
Force Production ◽  
Mdx Mouse ◽  
Mdx Mice ◽  
Dystrophic Muscle ◽  
Lengthening Contractions ◽  
Fast Twitch

We demonstrated that the susceptibility of skeletal muscle to injury from lengthening contractions in the dystrophin-deficient mdx mouse is directly linked with the extent of fiber branching within the muscles and that both parameters increase as the mdx animal ages. We subjected isolated extensor digitorum longus muscles to a lengthening contraction protocol of 15% strain and measured the resulting drop in force production (force deficit). We also examined the morphology of individual muscle fibers. In mdx mice 1–2 mo of age, 17% of muscle fibers were branched, and the force deficit of 7% was not significantly different from that of age-matched littermate controls. In mdx mice 6–7 mo of age, 89% of muscle fibers were branched, and the force deficit of 58% was significantly higher than the 25% force deficit of age-matched littermate controls. These data demonstrated an association between the extent of branching and the greater vulnerability to contraction-induced injury in the older fast-twitch dystrophic muscle. Our findings demonstrate that fiber branching may play a role in the pathogenesis of muscular dystrophy in mdx mice, and this could affect the interpretation of previous studies involving lengthening contractions in this animal.

scholarly journals Expression of insulin growth factor-1 splice variants and structural genes in rabbit skeletal muscle induced by stretch and stimulation

1999 ◽  
Vol 516 (2) ◽  
pp. 583-592 ◽  
Author(s):  
Godfrina McKoy ◽  
William Ashley ◽  
James Mander ◽  
Shi Yu Yang ◽  
Norman Williams ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Splice Variants ◽  
Rabbit Skeletal Muscle ◽  
Structural Genes ◽  
Insulin Growth Factor

scholarly journals Early metabolic changes measured by 1H MRS in healthy and dystrophic muscle after injury

2012 ◽  
Vol 113 (5) ◽  
pp. 808-816 ◽  
Author(s):  
Su Xu ◽  
Stephen J. P. Pratt ◽  
Espen E. Spangenburg ◽  
Richard M. Lovering
Keyword(s):  
Skeletal Muscle ◽  
Muscle Injury ◽  
Tibialis Anterior Muscle ◽  
Metabolic Changes ◽  
Mdx Mice ◽  
Resonance Spectroscopy ◽  
Dystrophic Muscle ◽  
1H Mrs ◽  
Skeletal Muscle Injury

Skeletal muscle injury is often assessed by clinical findings (history, pain, tenderness, strength loss), by imaging, or by invasive techniques. The purpose of this work was to determine if in vivo proton magnetic resonance spectroscopy (1H MRS) could reveal metabolic changes in murine skeletal muscle after contraction-induced injury. We compared findings in the tibialis anterior muscle from both healthy wild-type (WT) muscles (C57BL/10 mice) and dystrophic ( mdx mice) muscles (an animal model for human Duchenne muscular dystrophy) before and after contraction-induced injury. A mild in vivo eccentric injury protocol was used due to the high susceptibility of mdx muscles to injury. As expected, mdx mice sustained a greater loss of force (81%) after injury compared with WT (42%). In the uninjured muscles, choline (Cho) levels were 47% lower in the mdx muscles compared with WT muscles. In mdx mice, taurine levels decreased 17%, and Cho levels increased 25% in injured muscles compared with uninjured mdx muscles. Intramyocellular lipids and total muscle lipid levels increased significantly after injury but only in WT. The increase in lipid was confirmed using a permeable lipophilic fluorescence dye. In summary, loss of torque after injury was associated with alterations in muscle metabolite levels that may contribute to the overall injury response in mdx mice. These results show that it is possible to obtain meaningful in vivo 1H MRS regarding skeletal muscle injury.

scholarly journals ẢNH HƯỞNG CỦA HORMONE GROWTH VÀ INSULIN GROWTH FACTOR 1 ĐỐI VỚI SỰ TĂNG TRƯỞNG XƯƠNG THEO TRỤC DỌC

2020 ◽  
Vol 3 (5) ◽  
pp. 67-71
Author(s):  
Giang Trần Long
Keyword(s):  
Growth Factor ◽  
Insulin Growth Factor ◽  
Igf I

Hormone Growth (GH) và Insulin Growth Factor 1 (IGF-I) có vai trò quan trọng trong sự phát triển chiều cao cơ thể thông qua các tác động lên xương. Nhiều công trình nghiên cứu trên người và động vật cho thấy GH kích thích trực tiếp sự phát triển xương theo trục dọc bằng cách kích thích cácnguyên bào sụn trong đĩa tăng trưởng theo cơ chế nhân dòng vô tính và IGF -I kích thích các tế bào ở các giai đoạn sau bằng cách làm giảm thời gian chu kỳ tế bào. Ngoài ra, GH và IGF –I cũng phát huy tác động bổ trợ hoặc tương tác với nhau khi chúng được đưa vào cơ thể cùng nhau.

Increased carnitine palmitoyltransferase in cardiac myocytes is mediated by insulin growth factor I

1996 ◽  
Vol 271 (2) ◽  
pp. H422-H427 ◽  
Author(s):  
E. K. Hudson ◽  
D. Wang ◽  
L. L. Bieber ◽  
L. M. Buja ◽  
J. B. McMillin
Keyword(s):  
Growth Factor ◽  
Cardiac Myocytes ◽  
Mitochondrial Protein ◽  
Carnitine Palmitoyltransferase ◽  
Neonatal Rat ◽  
Heart Cells ◽  
Insulin Growth Factor ◽  
Igf I ◽  
High Concentrations ◽  
Cpt I

The mitochondrial carnitine palmitoyltransferase (CPT) system is composed of two proteins, CPT-I and -II, which, together with carnitine acylcarnitine translocase, are involved in the transport of fatty acids into the mitochondrial matrix for beta-oxidation. In the liver, CPT-I and its inhibition by malonyl-CoA are sensitive to hormonal (10(-9) M) levels of insulin; however, a similar effect of insulin on heart CPT is controversial. In cultured neonatal rat cardiac myocytes, tissue culture concentrations (1.7 microM) of insulin increase CPT and cytochrome oxidase activities as well as mitochondrial protein synthesis, suggesting that a growth mechanism may be involved. Because insulin at high concentrations may interact with the insulin-like growth factor (IGF-I) receptor, the consequences of insulin's action on heart cells in culture may be mediated through the IGF pathway. Consistent with an IGF-mediated pathway for the effect of insulin, incorporation of radioactivity into immunoprecipitated CPT-II from insulin-treated cardiac myocytes is dramatically increased over control cells. The amount of immunoreactive CPT-I is also increased in insulin-treated cells. Moreover, an IGF-I analogue that inhibits the autophosphorylation of the IGF-I receptor blunts the insulin-mediated increase in CPT-I and -II activities by > 70%. At low physiologically relevant concentrations (10 ng/ml), IGF-I significantly increases the activities of both CPT-I and -II, and the IGF-I analogue eliminates the IGF-I response. This is the first study to suggest involvement of the IGF-I pathway in the regulation of mitochondrial CPT synthesis and activities in the heart.

scholarly journals Protective Effect of Pyropia yezoensis Peptide on Dexamethasone-Induced Myotube Atrophy in C2C12 Myotubes

Marine Drugs ◽  
2019 ◽  
Vol 17 (5) ◽  
pp. 284 ◽  
Author(s):  
Min-Kyeong Lee ◽  
Jeong-Wook Choi ◽  
Youn Hee Choi ◽  
Taek-Jeong Nam
Keyword(s):  
Skeletal Muscle ◽  
Growth Factor ◽  
Signaling Pathway ◽  
Muscle Atrophy ◽  
Skeletal Muscle Atrophy ◽  
C2c12 Myotubes ◽  
Protective Effects ◽  
Factor I ◽  
Igf I ◽  
Foxo Signaling Pathway

Dexamethasone (DEX), a synthetic glucocorticoid, causes skeletal muscle atrophy. This study examined the protective effects of Pyropia yezoensis peptide (PYP15) against DEX-induced myotube atrophy and its association with insulin-like growth factor-I (IGF-I) and the Akt/mammalian target of rapamycin (mTOR)-forkhead box O (FoxO) signaling pathway. To elucidate the molecular mechanisms underlying the effects of PYP15 on DEX-induced myotube atrophy, C2C12 myotubes were treated for 24 h with 100 μM DEX in the presence or absence of 500 ng/mL PYP15. Cell viability assays revealed no PYP15 toxicity in C2C12 myotubes. PYP15 activated the insulin-like growth factor-I receptor (IGF-IR) and Akt-mTORC1 signaling pathway in DEX-induced myotube atrophy. In addition, PYP15 markedly downregulated the nuclear translocation of transcription factors FoxO1 and FoxO3a, and inhibited 20S proteasome activity. Furthermore, PYP15 inhibited the autophagy-lysosomal pathway in DEX-stimulated myotube atrophy. Our findings suggest that PYP15 treatment protected against myotube atrophy by regulating IGF-I and the Akt-mTORC1-FoxO signaling pathway in skeletal muscle. Therefore, PYP15 treatment appears to exert protective effects against skeletal muscle atrophy.

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