SS-31 does not prevent or reduce muscle atrophy 7 days after a 65 kdyne contusion spinal cord injury in young male mice

Boldine Alters Serum Lipidomic Signatures after Acute Spinal Cord Transection in Male Mice

Traumatic spinal cord injury (SCI) results in wide-ranging cellular and systemic dysfunction in the acute and chronic time frames after the injury. Chronic SCI has well-described secondary medical consequences while acute SCI has unique metabolic challenges as a result of physical trauma, in-patient recovery and other post-operative outcomes. Here, we used high resolution mass spectrometry approaches to describe the circulating lipidomic and metabolomic signatures using blood serum from mice 7 d after a complete SCI. Additionally, we probed whether the aporphine alkaloid, boldine, was able to prevent SCI-induced changes observed using these 'omics platforms'. We found that SCI resulted in large-scale changes to the circulating lipidome but minimal changes in the metabolome, with boldine able to reverse or attenuate SCI-induced changes in the abundance of 50 lipids. Multiomic integration using xMWAS demonstrated unique network structures and community memberships across the groups.

Assessing the impact of boldine on the gastrocnemius using multiomics profiling at 7 and 28 days post-complete spinal cord injury in young male mice

Spinal cord injury (SCI) results in rapid muscle loss. Exogenous molecular interventions to slow muscle atrophy after SCI have been relatively ineffective and require the search for novel therapeutic targets. Connexin hemichannels (CxHCs) allow nonselective passage of small molecules into and out of the cell. Boldine, a CxHC-inhibiting aporphine found in the boldo tree (Peumus boldus), has shown promising preclinical results in slowing atrophy during sepsis and restoring muscle function in dysferlinopathy. We administered 50 mg/kg/day of boldine to spinal cord transected mice beginning 3 days post-injury. Tissue was collected 7 and 28 days post-SCI and the gastrocnemius was used for multiomics profiling. Boldine did not prevent body or muscle mass loss but attenuated SCI-induced changes in the abundance of the amino acids proline, phenylalanine, leucine and isoleucine, as well as glucose, 7 days post-SCI. SCI resulted in the differential expression of ∼7,700 and ∼2,000 genes at 7 and 28 days, respectively, compared with Sham controls. Pathway enrichment of these genes highlighted ribosome biogenesis at 7 days and translation and oxidative phosphorylation at both timepoints. Boldine altered the expression of ∼150 genes at 7 days and ∼110 genes at 28 days post-SCI. Pathway enrichment of these genes indicated a potential role for boldine in suppressing protein ubiquitination and degradation at the 7-day timepoint. Methylation analyses showed minimal differences between groups. Taken together, boldine is not an efficacious therapy to preserve body and muscle mass after complete SCI, though it attenuated some SCI-induced changes across the metabolome and transcriptome.NEW & NOTEWORTHY This is the first study to describe the multiome of skeletal muscle paralyzed by a spinal cord injury (SCI) in mice across the acute and subacute timeframe after injury. We show large-scale changes in the metabolome and transcriptome at 7 days post-injury compared with 28 days. Furthermore, we show that the alkaloid boldine was able to prevent SCI-induced changes in muscle glucose and free amino acid levels at 7 days, but not 28 days, after SCI.

Elamipretide effects on the skeletal muscle phosphoproteome in aged female mice

The age-related decline in skeletal muscle mass and function is known as sarcopenia. Sarcopenia progresses based on complex processes involving protein dynamics, cell signaling, oxidative stress, and repair. We have previously found that 8-week treatment with elamipretide improves skeletal muscle function, reverses redox stress, and restores protein S-glutathionylation changes in aged female mice. This study tested whether 8-week treatment with elamipretide also affects global phosphorylation in skeletal muscle consistent with functional improvements and S-glutathionylation. Using female 6-7-month-old mice and 28-29-month-old mice, we found that phosphorylation changes did not relate to S-glutathionylation modifications, but that treatment with elamipretide did partially reverse age-related changes in protein phosphorylation in mouse skeletal muscle.