Elucidation of molecular and functional networks linked to sarcopenia prevention by caloric restriction in rhesus monkeys
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ABSTRACT: Caloric restriction (CR) improves survival in nonhuman primates and delays the onset of age-related morbidities including sarcopenia, the age-related loss of muscle mass and function. A shift in metabolism anticipates the onset of muscle aging phenotypes in nonhuman primates suggesting a potential role for metabolism in CR’s protective effects. Here we show that CR induced profound changes in muscle composition and the cellular metabolic environment. Bioinformatic analysis linked these adaptations to proteostasis, RNA processing, and lipid synthetic pathways. At the tissue level, CR maintained contractile content and attenuated age-related metabolic shifts among individual fiber types with higher mitochondrial activity, altered redox metabolism, and smaller lipid droplet size. Biometric and metabolic rate data confirm preserved metabolic efficiency in CR animals that correlated with attenuation of age-related muscle mass and physical activity. These data suggest that CR-induced reprogramming of metabolism plays a role in delayed aging of skeletal muscle in rhesus monkeys.
Project description:Sarcopenia is an age-associated loss of skeletal muscle mass and strength that increases the risk of disability. Calorie restriction (CR), the consumption of fewer calories while maintaining adequate nutrition, mitigates sarcopenia and many other age-related diseases. To identify potential mechanisms by which CR preserves skeletal muscle integrity during aging, we used mRNA-Seq for deep characterization of gene regulation and mRNA abundance in skeletal muscle of old mice compared with old mice subjected to CR. mRNA-Seq revealed complex CR-associated changes in expression of mRNA isoforms, many of which occur without a change in total message abundance and thus would not be detected by methods other than mRNA-Seq. Functional annotation of differentially expressed genes reveals CR-associated upregulation of pathways involved in energy metabolism and lipid biosynthesis, and downregulation of pathways mediating protein breakdown and oxidative stress, consistent with earlier microarray-based studies. CR-associated changes not noted in previous studies involved downregulation of genes controlling actin cytoskeletal structures and muscle development. These CR-associated changes reflect generally healthier muscle, consistent with CR’s mitigation of sarcopenia. mRNA-Seq generates a rich picture of the changes in gene expression associated with CR, and may facilitate identification of genes that are primary mediators of CR’s effects. Comprehensive survey of mRNA from skeletal muscle of mice subjected to calorie restricted or control diets using deep sequencing
Project description:Caloric Restriction (CR) extends lifespan and delays the onset of age-related disorders in diverse species. Metabolic regulatory pathways have been implicated in the mechanisms of CR, but the molecular details have not been elucidated. Here we show that CR engages RNA processing of genes associated with a highly integrated reprogramming of hepatic metabolism. We conducted molecular profiling of liver biopsies collected from adult male rhesus monkeys (Macaca mulatta) at baseline and after 2 years on control or CR (30% restricted) diet. Quantitation of over 20,000 molecules from the hepatic transcriptome, proteome, and metabolome, indicated that metabolism and RNA processing are major features of the response to CR. Predictive models identified lipid, branched chain amino acid, and short-chain carbon metabolic pathways, with alternate transcript use for over half of the genes in the CR network. We conclude that RNA-based mechanisms are central to the CR response and integral in metabolic reprograming.
Project description:The impact of chronic caloric restriction (CR) on health and survival in model organisms is complex and its underlying molecular mechanisms are poorly understood. Genetic background, sex, degree of CR and diet composition are expected modifiers of survival outcomes of this intervention. A recent study in mice addressed the impact of diet composition and feeding patterns used in nonhuman primates. It was found that, while diet composition alone did not impact longevity, fasting and calories were determinant for increased survival. We use here a combined physiological, multi-omics (transcriptomics-metabolomics), and integrated pathway analyses to gain insight into core and specific pathways associated with liver healthspan and lifespan. Main findings show that liver longevity pathways associated with CR predominantly correspond to detoxification, molecular turnover-repair-maintenance, and energy supply processes. Differential responses on lifespan extension provided by the different feeding strategies unveiled a distinct pattern of longevity pathways that centered around amino acid, fatty acid and nucleic acid metabolisms. Glycine-serine-threonine metabolism was a unique metabolic hub associated with lifespan whereas short-chain fatty acids and essential PUFAs metabolism were unique to healthspan. Nonhuman primate serum metabolomics data essentially recapitulated key features in mice.
Project description:Sarcopenia is an age-associated loss of skeletal muscle mass and strength that increases the risk of disability. Calorie restriction (CR), the consumption of fewer calories while maintaining adequate nutrition, mitigates sarcopenia and many other age-related diseases. To identify potential mechanisms by which CR preserves skeletal muscle integrity during aging, we used mRNA-Seq for deep characterization of gene regulation and mRNA abundance in skeletal muscle of old mice compared with old mice subjected to CR. mRNA-Seq revealed complex CR-associated changes in expression of mRNA isoforms, many of which occur without a change in total message abundance and thus would not be detected by methods other than mRNA-Seq. Functional annotation of differentially expressed genes reveals CR-associated upregulation of pathways involved in energy metabolism and lipid biosynthesis, and downregulation of pathways mediating protein breakdown and oxidative stress, consistent with earlier microarray-based studies. CR-associated changes not noted in previous studies involved downregulation of genes controlling actin cytoskeletal structures and muscle development. These CR-associated changes reflect generally healthier muscle, consistent with CR’s mitigation of sarcopenia. mRNA-Seq generates a rich picture of the changes in gene expression associated with CR, and may facilitate identification of genes that are primary mediators of CR’s effects.
Project description:Calorie restriction (CR) is the most robust non-genetic intervention to universally delay the onset of age-related diseases and extend mean and maximum lifespan. However, species, strain, sex, diet, age of onset, and level of CR are emerging as important variables to consider for a successful CR response. Here, we investigated the role of strain, sex and level of CR on outcomes of health and survival in mice. Response to CR varied from lifespan extension to no effect on survival, while consistently delaying the onset and impact of diseases independently of strain, sex and level of dietary restriction. CR led to transcriptional and metabolomics changes in the liver indicating anaplerotic filling of the Krebs cycle together with fatty acid fueling of mitochondria. Additionally, CR prevented the age-associated decline in the proteostasis network. Further, CR increased mitochondrial number and preserved their ultrastructure and function with age. Abrogation of mitochondrial function by deletion of fumarate hydratase or malate dehydrogenase 2 negated the life-prolonging effects of CR in yeast and worms. In F1 hybrid strains of mice, the lifespan response to CR tracked with the dam, indicating that the mitochondrial haplotype is an important regulator of CR. Our data illustrate the complexity of the CR responses within a single animal species in the context of aging, with a clear separation of outcomes related to health and survival, highlighting the complexities of translation of CR into human interventions. The study examines the effects of sex (male/female), mouse strain (DBA2/J versus C57BL/J), and diet (Ad libitum, 20% caloric restriction (20%CR), or 40%CR) using six biological replicate samples per group.
Project description:Calorie restriction (CR) is the most robust non-genetic intervention to universally delay the onset of age-related diseases and extend mean and maximum lifespan. However, species, strain, sex, diet, age of onset, and level of CR are emerging as important variables to consider for a successful CR response. Here, we investigated the role of strain, sex and level of CR on outcomes of health and survival in mice. Response to CR varied from lifespan extension to no effect on survival, while consistently delaying the onset and impact of diseases independently of strain, sex and level of dietary restriction. CR led to transcriptional and metabolomics changes in the liver indicating anaplerotic filling of the Krebs cycle together with fatty acid fueling of mitochondria. Additionally, CR prevented the age-associated decline in the proteostasis network. Further, CR increased mitochondrial number and preserved their ultrastructure and function with age. Abrogation of mitochondrial function by deletion of fumarate hydratase or malate dehydrogenase 2 negated the life-prolonging effects of CR in yeast and worms. In F1 hybrid strains of mice, the lifespan response to CR tracked with the dam, indicating that the mitochondrial haplotype is an important regulator of CR. Our data illustrate the complexity of the CR responses within a single animal species in the context of aging, with a clear separation of outcomes related to health and survival, highlighting the complexities of translation of CR into human interventions.
Project description:Calorie restriction (CR) improved healthspan in two longitudinal studies in nonhuman primates (NHPs), yet only the University of Wisconsin (UW) study demonstrated an increase in survival in CR monkeys relative to controls; the National Institute on Aging (NIA) study did not. Here, analysis of left ventricle samples showed that CR did not reduce cardiac fibrosis relative to controls. However, there was a 5.9-fold increase of total fibrosis in UW hearts, compared to NIA. Diet composition was a prominent difference between the studies; therefore, we used the NHP diets to characterize diet-associated molecular and functional changes in the hearts of mice. Consistent with the findings from the NHP samples, mice fed UW or a modified NIA diet with increased sucrose and fat developed greater cardiac fibrosis compared to the NIA diet, and transcriptomics analysis revealed diet-induced activation of myocardial oxidative phosphorylation and cardiac muscle contraction pathways.
Project description:Abstract Background: The prevalence of sarcopenia is increasing and effective interventions are required to prevent or reverse age-related muscle loss. However it is often challenging expensive and time-consuming to develop and test the effectiveness of such interventions. Furthermore translational animal models that adequately mimic underlying physiological pathways are scarce. Strong predictors for the incidence of sarcopenia include a sedentary life-style and malnutrition. Therefore our objective was to investigate the translational value of three potential mouse models for sarcopenia namely partial immobilized caloric restricted (CR) and a combination (immobilized & CR) model. Methods: C57BL/6J mice were calorically restricted (-40%) and/or one hindleg was immobilized for two weeks to induce loss of muscle mass and function. Muscle mass function and diameter and distribution of slow (type 1) and fast ( type 2) myofibers were compared to those of young control (4 months) and old reference mice (21 months). Transcriptome analysis of quadriceps muscle was performed to identify underlying pathways and were compared with those being expressed in aged human vastus lateralis muscle-biopsies using a meta-analysis of five different human studies. Results: Caloric restriction induced overall loss of lean body mass (-15% p<0.001) whereas immobilization decreased muscle strength (-28% p<0.001) and muscle mass of hindleg muscles specifically (on average -25% p<0.001). The proportion of slow myofibers increased with aging in mice (+5% p<0.05) and this was not recapitulated by the CR and/or immobilization models. The diameter of fast myofibers decreased with aging (-7% p<0.05) and this was mimicked by all models. Transcriptome analysis revealed that the combination of CR and immobilization recapitulated more pathways characteristic for human muscle-aging (73%) than naturally aged (21 months old) mice (45%). These pathways included critical pathways relevant for protein synthesis/ breakdown (mitochondrial) metabolism neurology and the vascular system. Conclusions: The combination model exhibits loss of both muscle mass (due to CR) and function (due to immobilization) and has a remarkable similarity with pathways underlying human sarcopenia. Our results demonstrate that naturally aging up to 21 months in mice only partially recapitulates the human pathology with fewer overlapping pathways than the combination model. These findings underline that external factors such as sedentary behavior and malnutrition are key elements of a translational mouse model and favor the combination model as a rapid model for testing the treatments against sarcopenia.
Project description:Sarcopenia is a disease involving extensive loss of muscle mass and strength with age and is a major cause of disability and accidents in the elderly. Mechanisms purported to be involved in muscle ageing and sarcopenia are numerous but poorly understood, necessitating deeper study. Hence, we employed high-throughput RNA sequencing to explicate the global changes in protein-coding gene expression occurring in skeletal muscle with age. Caloric restriction (CR) is a proven prophylactic intervention against sarcopenia. Therefore, total RNA was isolated from the muscle tissue of both rats fed ad libitum and CR rats. Collected data were subjected to Gene Ontology, pathway, co-expression, and interaction network analyses. This revealed the functional pathways most activated by both ageing and CR, as well as the key “hub” proteins involved in their activation. RNA-seq revealed 442 protein-coding genes to be upregulated and 377 to be downregulated in aged muscle, compared to young muscle. Upregulated genes were commonly involved in protein folding and the immune response; meanwhile, downregulated genes were often related to developmental biology. CR was found to suppress 69.7% and rescue 57.8% of the genes found to be upregulated and downregulated in aged muscle, respectively. In addition, CR uniquely upregulated 291 and downregulated 304 protein-coding genes. Hub genes implicated in both ageing and CR included Gc, Plg, Irf7, Ifit3, Usp18, Rsad2, Blm and RT1-A2, whilst those exclusively implicated in CR responses included Alb, Apoa1, Ambp, F2, Apoh, Orm1, Mx1, Oasl2 and Rtp4. Hub genes involved in ageing but unaffected by CR included Fgg, Fga, Fgb and Serpinc1. In conclusion, this comprehensive RNA sequencing study highlighted gene expression patterns, hub genes and signalling pathways most affected by ageing in skeletal muscle. This data may provide the initial evidence for several targets for therapeutic interventions against sarcopenia.