Project description:Prolonged fasting-induced changes in rat tibialis anterior muscle transcriptome Skeletal muscle is of primary importance for metabolism, thermogenesis and locomotion. However, muscle integrity is inevitably challenged throughout life, and muscle atrophy occurs in various situations, being associated with development of metabolic diseases. There is virtually no fully effective countermeasure today to fight the loss of muscle mass. It is therfore needed to understand in depth how muscle mass is regulated in wasting conditions. The aim of this study was to decipher the transcriptional regulations involved in prolonged fasting-induced muscle wasting during the phase of protein sparing (P2) and the late phase of increased body protein mobilization (P3). The main findings show that gene expression changes reflect well the intense use of lipids as fuels during P2 and increased use of muscle proteins during P3. Changes in muscle transcriptome for downstream signaling of anabolic and catabolic hormones (Smad, NFKB, EiF2alpha-ATF4, autophagy, ubiquitin-proteasome, Foxo, AMPK, PI3K/AKT, and mTOR pathways) and for the response to oxidative stress, transcription and translation processes, and myogenesis are generally consistent with increased muscle protein degradation and repressed synthesis, in a more marked manner during P3 than P2 compared to the fed state. Nevertheless, several changes appeared to be in favour of muscle protein synthesis during fasting, notably at the level of PI3K/AKT and mTOR pathways, transcription and translations processes, and the response to oxidative stress. They could constitute mechanisms that promote protein sparing during P2 and anticipate refeeding during P3 for restoration of the protein compartment. Future studies should examine validity of such targets for improving nitrogen balance during catabolic diseases.
Project description:Skeletal muscle accounts for the largest proportion of human body mass, on average, and is a key tissue in complex diseases and mobility. It is composed of several different cell and muscle fiber types. Here, we optimize single-nucleus ATAC-seq (snATAC-seq) to map skeletal muscle cell-specific chromatin accessibility landscapes in frozen human and rat samples, and single-nucleus RNA-seq (snRNA-seq) to map cell-specific transcriptomes in human. We additionally perform multi-omics profiling (gene expression and chromatin accessibility) on human and rat muscle samples.
Project description:Skeletal muscle in fish presents a high plasticity controlled by a dynamic balance between anabolic and catabolic signaling pathways. Decreased food availability can inhibit muscle growth and trigger muscle catabolism pathways, thu promoting muscle atrophy. In contrast, anabolism may be favored during restoration of food supply, promoting the muscle growth. Considering this, we analyzed fast-twitch muscle of juvenile Piaractus mesopotamicus (pacu) submitted to a prolonged fasting (30 days) and refeeding (up to 30 days) using shotgun proteomics and gene expression analysis. The relative rate of weight and length increase, as well as the expression of mafbx and igf -1 genes, suggest that prolonged fasting caused muscle atrophy and that 30 days of refeeding led to partial compensatory growth. Shotgun proteomics analysis identified 99 proteins after fasting and 71 proteins after refeeding periods, of which 23 and 17 were differentially expressed after fasting and after 30 days of refeeding, respectively. Most of these differentially expressed proteins were related to cytoskeleton, muscle contraction and muscle metabolism. Among these, parvalbumin (PVALB), a calcium-binding protein and food allergen, was selected for further RT-qPCR analysis, which showed that pvalb mRNA was not changed after 30 days of fasting and 30 days of refeeding, but it was downregulated after 6h and 24h of refeeding. This suggests a post-transcriptional regulation of PVALB in fish muscle. In conclusion, our results suggest that muscle atrophy and partial compensatory growth caused by prolonged fasting and refeeding affected the muscle proteome and PVALB expression. Our results can contribute to the understanding of muscle anabolic and catabolic pathways in response to changes in food availability.
Project description:Fasting increases the level of skeletal muscle ATF4 mRNA, which promotes skeletal myofiber atrophy. To begin to determine the mechanism of ATF4-mediated myofiber atrophy, we compared the effects of fasting and ATF4 overexpression on global skeletal muscle mRNA expression in C57BL/6 mice.
Project description:The goal of these studies was to determine the effects of fasting on skeletal muscle mRNA levels in healthy human subjects. Seven healthy adult human subjects fasted for 40 hours and then a muscle biopsy (fasting sample) was obtained from the vastus lateralis muscle. Immediately after the first muscle biospy, subjects then ate a mixed meal. Six hours after the first muscle biopsy, a second muscle biopsy (fed sample) was obtained from the contralateral vastus lateralis muscle. In each subject, mRNA levels under fasting conditions were normalized to mRNA levels under fed conditions, which were set at 1.
Project description:The aim of the study was to investigate how short-term fasting affects whole-body energy homeostasis and skeletal muscle energy/nutrient-sensing pathways and transcriptome in humans. For this purpose, twelve young healthy men were studied during a 24-hour fast. Skeletal muscle biopsies were collected and analyzed at baseline and after 4, 10 and 24h of fasting. As expected, fasting induced a time-dependent decrease in plasma insulin and leptin levels, whereas levels of ketone bodies and free fatty acids increased. This was associated with a metabolic shift from glucose towards lipid oxidation. Transcriptome profiling identified genes that were significantly regulated by fasting in skeletal muscle at both early and late time-points. Collectively, our study provides a comprehensive map of the main energy/nutrient-sensing pathways and transcriptomic changes during short-term adaptation to fasting in human skeletal muscle
Project description:Northern elephant seals (NES, Mirounga angustirostris) undergo an annual molt during which they spend ~40 days fasting on land with reduced activity and lose approximately one-quarter of their body mass. Reduced activity and muscle load in stereotypic terrestrial mammalian models results in decreased muscle mass and capacity for force production and aerobic metabolism. However, the majority of lost mass in fasting female NES is from fat while muscle mass is largely preserved. Although muscle mass is preserved, potential changes to the metabolic and contractile capacity are unknown. To assess potential changes in NES skeletal muscle during molt, we collected muscle biopsies from 6 adult female NES at the beginning of the molt and after ~30 days at the end of the molt. Skeletal muscle was assessed for respiratory capacity using high resolution respirometry, and RNA was extracted to assess changes in gene expression. Despite a month of reduced activity, fasting, and weight loss, skeletal muscle respiratory capacity was preserved with no change in OXPHOS respiratory capacity. Molt was associated with 162 upregulated genes including genes favoring lipid metabolism and regulating cell cycles. We identified 172 downregulated genes including those coding for ribosomal proteins and genes associated with skeletal muscle force transduction and glucose metabolism. Following ~30 days of molt, NES skeletal muscle metabolic capacity appears largely preserved although mechanotransduction may be compromised. In the absence of exercise stimulus, fasting-induced shifts in skeletal muscle lipid metabolism may stimulate lipid signaling pathways associated with preserving the mass and metabolic capacity of slow oxidative muscle.
Project description:a genomic profile of aged rat sceletal muscle with diffrent degrees of sensorimotor disturbances. Keywords: age skeletal muscle sensorimotor disturbances
Project description: In fish, the slow-twitch skeletal muscle fibres have an oxidative metabolism, present peripherical location in the red muscle, and are used for sustained movements. They may respond to alterations in food availability differently than the fast-twitch muscle. The aim of this manuscript was to study the slow-twitch muscle fibres of Piaractus Mesopotamicus, a neotropical fish, submitted to 30 days of fasting (D30) followed by one day (D31) or 30 days of refeeding (D60). The treated animals were compared with regularly fed fish. To verify the presence of atrophy and hypertrophy, we performed histological analysis of muscle fibre diameter in D30 and D60, and RT-qPCR gene expression analysis of catabolic (murfa, murfb, mafbx) and anabolic genes (igf-1, mTOR) in D30, D31 and D60. The gene expression of the allergen and Ca2+-carrier parvalbumin (pvalb) was also measured in D30, D31 and D60. The proteome of slow-twitch fibres at D30 and D60 was obtained by shotgun proteomics (digestion of proteins with trypsin followed by LC-MS/MS identification), and the proteins differentially expressed were used to construct protein interaction networks. The histological analysis showed no difference between treated fish in relation to the control. The expression of catabolic and anabolic genes was not changed, except for the negative regulation of igf-1 in D30 and of mtor in D31. The expression of pvalb was not changed in D30 and D60, but it was decreased in D31. The proteomic analysis identified 169 proteins in D30 (24 upregulated and 18 downregulated) and 170 proteins in D60 (17 upregulated and 21 downregulated). Many of them were related to energetic metabolism, including lipid metabolism, as shown by the protein network analysis. These results enlarge our understanding of the acclimation of slow-twitch fibres to changes in nutrient availability and set a path for future research.