metallothionein and Muscular-Atrophy

Metallothioneins are proteins that are involved in intracellular zinc storage and transport. Their expression levels have been reported to be elevated in several settings of skeletal muscle atrophy. We therefore investigated the effect of metallothionein blockade on skeletal muscle anabolism

Topics: Animals; Biomarkers; Body Weight; Cell Size; Gene Silencing; Glucocorticoids; Humans; Hypertrophy; Metallothionein; Mice; Muscle Development; Muscle Fibers, Skeletal; Muscle Strength; Muscle, Skeletal; Muscular Atrophy; Organ Size; Proto-Oncogene Proteins c-akt; Rats; Sarcopenia; Signal Transduction; TOR Serine-Threonine Kinases; Up-Regulation; Zinc

Skeletal muscle atrophy is a significant health problem that results in decreased muscle size and function and has been associated with increases in oxidative stress. The molecular mechanisms that regulate muscle atrophy, however, are largely unknown. The metallothioneins (MT), a family of genes with antioxidant properties, have been found to be consistently upregulated during muscle atrophy, although their function during muscle atrophy is unknown. Therefore, we hypothesized that MT knockdown would result in greater oxidative stress and an enhanced atrophy response in C(2)C(12) myotubes subjected to serum reduction (SR), a novel atrophy-inducing stimulus. Forty-eight hours before SR, myotubes were transfected with small interfering RNA (siRNA) sequences designed to decrease MT expression. Muscle atrophy and oxidative stress were then measured at baseline and for 72 h following SR. Muscle atrophy was quantified by immunocytochemistry and myotube diameter measurements. Oxidative stress was measured using the fluorescent probe 5-(and-6)-carboxy-2',7'-dichlorodihydrofluorescein. SR resulted in a significant increase in oxidative stress and a decrease in myotube size and protein content. However, there were no differences observed in the extent of muscle atrophy or oxidant activity following MT knockdown. We therefore conclude that the novel SR model results in a strong atrophy response and an increase in oxidant activity in cultured myotubes and that knockdown of MT does not affect that response.

Topics: Animals; Cell Line; Gene Knockdown Techniques; Hypertrophy; Immunohistochemistry; Metallothionein; Mice; Muscle Fibers, Skeletal; Muscle Proteins; Muscular Atrophy; Oxidants; Oxidative Stress; RNA Interference; Serum; Time Factors; Transfection

In this study skeletal muscles from 1.5- and 10-month-old Cu/Zn superoxide dismutase (SOD1) homozygous knockout (JLSod1(-/-)) mice obtained from The Jackson Laboratory (C57Bl6/129SvEv background) were compared with muscles from age- and sex-matched heterozygous (JLSod1(+/-)) littermates. The results of this study were compared with previously published data on two different strains of Sod1(-/-) mice: one from Dr. Epstein's laboratory (ELSod1(-/-); C57Bl6 background) and the other from Cephalon, Inc. (CSod1(-/-); 129/CD-1 background). Grouping of succinate dehydrogenase-positive fibers characterized muscles of Sod1(-/-) mice from all three strains. The 10-month-old Sod1(-/-)C and JL mice displayed pronounced denervation of the gastrocnemius muscle, whereas the ELSod1(-/-) mice displayed a small degree of denervation at this age, but developed accelerated age-related denervation later on. Denervation markers were up-regulated in skeletal muscle of 10-month-old JLSod1(-/-) mice. This study is the first to show that metallothionein mRNA and protein expression was up-regulated in the skeletal muscle of 10-month-old JLSod1(-/-) mice and was mostly localized to the small atrophic muscle fibers. In conclusion, all three strains of Sod1(-/-) mice develop accelerated age-related muscle denervation, but the genetic background has significant influence on the progress of denervation.

Topics: Aging; Animals; Female; Male; Metallothionein; Mice; Mice, Knockout; Mice, Transgenic; Muscle Denervation; Muscle, Skeletal; Muscular Atrophy; RNA, Messenger; Superoxide Dismutase; Superoxide Dismutase-1; Up-Regulation

Metallothionein (MT) is a small molecular weight protein possessing metal binding and free radical scavenging properties. We hypothesized that MT-1/MT-2 null (MT(-/-)) mice would display exacerbated soleus muscle atrophy, oxidative injury, and contractile dysfunction compared with the response of wild-type (WT) mice following acute spinal cord transection (SCT). Four groups of mice were studied: WT laminectomy, WT transection, MT(-/-) laminectomy (MT(-/-) lami), and MT(-/-) transection (MT(-/-) trans). Laminectomy animals served as surgical controls. Mice in SCT groups experienced similar percent body mass (BM) losses at 7 days postinjury. Soleus muscle mass (MM) and MM-to-BM ratio were lower at 7 days postinjury in SCT vs. laminectomy mice, with no differences observed between strains. However, soleus muscles from MT(-/-) trans mice showed reduced maximal specific tension compared with MT(-/-) lami animals. Mean cross-sectional area (microm(2)) of type I and type IIa fibers decreased similarly in SCT groups compared with laminectomy controls, and no difference in fiber distribution was observed. Lipid peroxidation (4-hydroxynoneal) was greater in MT(-/-) trans vs. MT(-/-) lami mice, but protein oxidation (protein carbonyls) was not altered by MT deficiency or SCT. Expression of key antioxidant proteins (catalase, manganese, and copper-zinc superoxide dismutase) was similar between the groups. In summary, MT deficiency did not impact soleus MM loss, but resulted in contractile dysfunction and increased lipid peroxidation following acute SCT. These findings suggest a role of MT in mediating protective adaptations in skeletal muscle following disuse mediated by spinal cord injury.

Topics: Acute Disease; Animals; Antioxidants; Catalase; Disease Models, Animal; Laminectomy; Lipid Peroxidation; Male; Metallothionein; Mice; Mice, Knockout; Muscle Contraction; Muscle Fibers, Fast-Twitch; Muscle Fibers, Slow-Twitch; Muscle Strength; Muscle, Skeletal; Muscular Atrophy; Oxidative Stress; Protein Carbonylation; Spinal Cord Injuries; Superoxide Dismutase; Thoracic Vertebrae

Topics: Animals; Humans; Metallothionein; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Oxidative Stress; Peptide Hydrolases; Rats; Restraint, Physical

Topics: Animals; Antioxidants; Calpain; Disease Models, Animal; Humans; Immobilization; Metallothionein; Muscle Proteins; Muscle, Skeletal; Muscular Atrophy; Oxidative Stress; Peptide Hydrolases; Proteasome Endopeptidase Complex; Spinal Cord Injuries; Time Factors; Ubiquitin; Ubiquitin-Protein Ligases

Skeletal muscle atrophy is a debilitating response to starvation and many systemic diseases including diabetes, cancer, and renal failure. We had proposed that a common set of transcriptional adaptations underlie the loss of muscle mass in these different states. To test this hypothesis, we used cDNA microarrays to compare the changes in content of specific mRNAs in muscles atrophying from different causes. We compared muscles from fasted mice, from rats with cancer cachexia, streptozotocin-induced diabetes mellitus, uremia induced by subtotal nephrectomy, and from pair-fed control rats. Although the content of >90% of mRNAs did not change, including those for the myofibrillar apparatus, we found a common set of genes (termed atrogins) that were induced or suppressed in muscles in these four catabolic states. Among the strongly induced genes were many involved in protein degradation, including polyubiquitins, Ub fusion proteins, the Ub ligases atrogin-1/MAFbx and MuRF-1, multiple but not all subunits of the 20S proteasome and its 19S regulator, and cathepsin L. Many genes required for ATP production and late steps in glycolysis were down-regulated, as were many transcripts for extracellular matrix proteins. Some genes not previously implicated in muscle atrophy were dramatically up-regulated (lipin, metallothionein, AMP deaminase, RNA helicase-related protein, TG interacting factor) and several growth-related mRNAs were down-regulated (P311, JUN, IGF-1-BP5). Thus, different types of muscle atrophy share a common transcriptional program that is activated in many systemic diseases.

Topics: Adenosine Triphosphate; Animals; Extracellular Matrix Proteins; Gene Expression Profiling; Gene Expression Regulation; Metallothionein; Mice; Muscle, Skeletal; Muscular Atrophy; Nitrogen; Protein Biosynthesis; Proteins; Rats; RNA, Messenger; Transcription Factors; Transcription, Genetic; Ubiquitin-Protein Ligases