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Proteomic identification of seasonally expressed proteins contributing to heart function and the avoidance of skeletal muscle disuse atrophy in a hibernating mammal

ABSTRACT: Hibernation in mammals such as the thirteen-lined ground squirrel (Ictidomys tridecemlineatus) takes place over 4 to 6 months and is characterized by multi-day bouts of hypothermic torpor (5-7 °C core body temperature) that are regularly interrupted every 1-2 weeks by brief (12-24 hour) normothermic arousal periods called interbout arousals. The goal of our work was to identify the molecular mechanisms which underlie the hibernator’s ability to preserve heart function and avoid the deleterious effects of skeletal muscle disuse atrophy over prolonged periods of inactivity, starvation, and near-freezing body temperatures. To achieve this goal, we performed organelle enrichment of heart and skeletal muscle at five seasonal time points followed by LC-MS-based label-free quantitative proteomics. In both organs we saw a dramatic increase in levels of many proteins as ground squirrels transition from an active state in September to a pre-hibernation state in October. Interestingly, seasonal abundance patterns also identified new candidates for mitigating disuse atrophy in skeletal muscle which include higher levels of DHRS7C, SRL, and RTN2 in December-January torpid, IBA, and March active animals; and higher March active levels of TRIM72 and MPZ. Elevation of these proteins prompted us to perform an ex vivo contractile mechanics analysis of both type 1 (soleus) and type 2 (extensor digitorum longus) muscles in fall active, torpid, and spring active animals. Consistent with our hypotheses, both muscle types showed no deleterious effects despite several months of sedentary activity that would normally result in reduced muscle performance in non-hibernating mammals. An increased understanding of protein expression in natural hibernators may enable novel therapeutic strategies to treat human health concerns such as muscle disuse atrophy and heart disease.

INSTRUMENT(S): Xevo G2-XS QTof

ORGANISM(S): Spermophilus Tridecemlineatus (thirteen-lined Ground Squirrel)

TISSUE(S): Quadriceps, Heart

SUBMITTER: James Checco

LAB HEAD: James Checco

PROVIDER: PXD044532 | Pride | 2023-12-21

REPOSITORIES: Pride

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Project description:Hibernation is energy saving adaptation involving suppression of activity to survive in highly seasonal environments. Immobility and disuse generate muscle loss in most mammalian species. In contrast to other mammals, bears and ground squirrels demonstrate limited muscle atrophy over the physical inactivity of winter hibernation. This suggests that hibernating mammals have adaptive mechanisms to prevent disuse muscle atrophy. To identify common transcriptional program underlying molecular mechanisms preventing muscle loss, we conducted a large-scale gene expression screening in hind limb muscles comparing hibernating and summer active black bears and arctic ground squirrels by the use of custom 9,600 probe cDNA microarrays. The molecular pathway analysis showed an elevated proportion of overexpressed genes involved in all stages of protein biosynthesis and ribosome biogenesis in muscle of both species during hibernation that implies induction of translation at different hibernation states. The induction of protein biosynthesis likely contributes to attenuation of disuse muscle atrophy through prolonged periods of immobility and starvation. This adaptive mechanism allows hibernating mammals to maintain full musculoskeletal function and preserve mobility during and immediately after hibernation, thus promoting survival. The lack of directional changes in genes of protein catabolic pathways does not support the importance of metabolic suppression for preserving muscle mass during winter. Coordinated reduction of multiply genes involved in oxidation reduction and glucose metabolism detected in both species is consistent with metabolic suppression and lower energy demand in skeletal muscle during inactivity of hibernation. Black bears sampled during winter hibernation were compared with the animals sampled during summer. Muscle tissue were hybridized on a custom 12,800 cDNA probe nylon membrane microarray platform . Six hibernating and six summer active bears were studied in the experiment.

Project description:Hibernation is energy saving adaptation involving suppression of activity to survive in highly seasonal environments. Immobility and disuse generate muscle loss in most mammalian species. In contrast to other mammals, bears and ground squirrels demonstrate limited muscle atrophy over the physical inactivity of winter hibernation. This suggests that hibernating mammals have adaptive mechanisms to prevent disuse muscle atrophy. To identify common transcriptional program underlying molecular mechanisms preventing muscle loss, we conducted a large-scale gene expression screening in hind limb muscles comparing hibernating and summer active black bears and arctic ground squirrels by the use of custom 9,600 probe cDNA microarrays. The molecular pathway analysis showed an elevated proportion of overexpressed genes involved in all stages of protein biosynthesis and ribosome biogenesis in muscle of both species during hibernation that implies induction of translation at different hibernation states. The induction of protein biosynthesis likely contributes to attenuation of disuse muscle atrophy through prolonged periods of immobility and starvation. This adaptive mechanism allows hibernating mammals to maintain full musculoskeletal function and preserve mobility during and immediately after hibernation, thus promoting survival. The lack of directional changes in genes of protein catabolic pathways does not support the importance of metabolic suppression for preserving muscle mass during winter. Coordinated reduction of multiply genes involved in oxidation reduction and glucose metabolism detected in both species is consistent with metabolic suppression and lower energy demand in skeletal muscle during inactivity of hibernation. Arctic ground squirrels sampled during winter hibernation were compared with the animals sampled during summer. Muscle was hybridized on a custom 9,600 probes nylon membrane microarray platform. Ten in late torpor, four in early arousal, then in late arousal were studied in experiments.

Project description:Loss of muscle proteins and the consequent weakness has important clinical consequences in diseases such as cancer, diabetes, chronic heart failure and in ageing. In fact, excessive proteolysis causes cachexia, accelerates disease progression and worsens life expectancy. Muscle atrophy involves a common pattern of transcriptional changes in a small subset of genes named atrophy-related genes or atrogenes. Whether microRNAs play a role in the atrophy program and muscle loss is debated. To understand the involvement of miRNAs in atrophy we performed miRNA expression profiling of mouse muscles under wasting conditions such as fasting, denervation, diabetes and cancer cachexia. We found that the miRNA signature is peculiar of each catabolic condition. We then focused on denervation and we revealed that changes in transcripts and microRNAs expression did not occur simultaneously but were shifted. Indeed, while the transcriptional control of the atrophy-related genes peaks at 3 days, the changes of miRNA expression maximised at 7 days after denervation. Among the different miRNAs, microRNA-206 and 21 were the most induced in denervated muscles. We characterized their pattern of expression and defined their role in muscle homeostasis. Indeed, in vivo gain and loss of function experiments revealed that miRNA-206 and miRNA-21 were sufficient and required for atrophy program. In silico and in vivo approaches identified the transcription factor YY1 and the translational initiator factor eIF4E3 as downstream targets of these miRNAs. Thus miRNAs are important for the fine-tuning of the atrophy program and their modulation can be a novel potential therapeutic approach to counteract muscle loss and weakness in catabolic conditions. To determine which miRNAs are relevant for the atrophic process, we performed miRNA expression profiles of muscles from different atrophic models (starvation, denervation and streptozotocin-induced diabetes). We checked whether there was a common signature of miRNA expression in different atrophying conditions and we found that every catabolic situation require a peculiar pattern of miRNA. We further focus on the condition of denervation and identified the most up-regulated miRNAs in this condition, miRNA-206 and miRNA-21.

Project description:Belt electrode-skeletal muscle electrical stimulation (B-SES) involves the use of belt-shaped electrodes to simultaneously contract multiple muscle groups. Twitch contractions have been demonstrated to protect against denervation-induced muscle atrophy in rats, possibly via mitochondrial biosynthesis. In this study, we examined whether inducing tetanus contractions with B-SES suppresses muscle atrophy and identified the underlying molecular mechanisms. We evaluated the effects of acute (60 Hz, 5 min) and chronic (60 Hz, 5 min, every alternate day for 1 week) B-SES on the tibialis anterior (TA) and gastrocnemius (GAS) muscles in Sprague Dawley rats using belt electrodes attached to both ankle joints. In acute stimulation, a significant decrease in glycogen content in the left and right TA and GAS was observed, suggesting that B-SES causes simultaneous contractions in multiple muscle groups. B-SES also enhanced p70S6K phosphorylation, an indicator of the mechanistic target of rapamycin complex 1 activity. During chronic stimulations, rats were divided into control (CONT), denervation-induced atrophy (DEN), and DEN+electrically stimulated with B-SES (DEN＋ES) groups. After 7 days of treatment, muscle wet weight (n = 8-11 for each group) and muscle fiber cross-sectional area (CSA, n = 6 for each group) of the TA and GAS muscles were reduced in the DEN and DEN+ES groups compared to those in the CON group. The DEN+ES group showed significantly higher muscle weight and CSA than the DEN group. Although RNA-seq and pathway analysis suggested that mitochondrial and ribosome biogenesis are key events in this phenomenon, mitochondrial content showed no difference. In contrast, ribosomal RNA 28S and 45S (n = 6) levels in the DEN+ES group were higher than those in the DEN group. The mRNA levels of the muscle proteolytic molecules Atrogin-1 and MuRF1 were significantly higher in DEN than in CONT but were suppressed in DEN+ES. In conclusion, tetanic electrical stimulation of both ankles using belt electrodes was effective in preventing denervation-induced atrophy in multiple muscle groups. Unlike twitch contractions, ribosomal biosynthesis plays a key role in tetanic contractions to prevent muscle atrophy.

			Action	DRS
	20211201_GS_SRQ10.mgf	Mgf
	20211201_GS_SRQ10.raw.rar	Raw
	20211201_GS_SRQ11.mgf	Mgf
	20211201_GS_SRQ11.raw.rar	Raw
	20211201_GS_SRQ12.mgf	Mgf

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Proteomic identification of seasonally expressed proteins contributing to heart function and the avoidance of skeletal muscle disuse atrophy in a hibernating mammal

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