Skeletal Muscle Gene Expression Profile in Response to Caloric Restriction and Aging: A Role for SirT1

Testosterone Modulation of Muscle Transcriptomic Profile During Lifestyle Therapy in Older Men with Obesity and Hypogonadism

BACKGROUND

Testosterone replacement therapy (TRT) added to lifestyle therapy can mitigate weight-loss-induced reduction of muscle mass and bone mineral density (BMD) in older men with obesity and hypogonadism.

OBJECTIVE

To investigate the molecular mechanisms underlying the attenuation of muscle and BMD loss in response to TRT during intensive lifestyle intervention in this high-risk older population.

METHODS

Among 83 older (≥ 65 years) men with obesity (BMI ≥ 30 kg/m2) and hypogonadism (early AM testosterone persistently < 300 ng/dL) associated with frailty (Modified Physical Performance Test score ≤ 31) randomized into 26-week lifestyle therapy plus testosterone (LT+TRT) or placebo (LT+Pbo) in the LITROS trial, 38 underwent serial muscle biopsies for the muscle transcriptomics substudy.

RESULTS

Despite similar ~10% weight loss, lean body mass and thigh muscle volume decreased less in LT+TRT than LT+Pbo (-2% vs. -4%, respectively; p = 0.04). Hip BMD was preserved in LT+TRT compared with LT+Pbo (0.4% vs. -1.3%; p = 0.03). Muscle strength increased similarly in LT+TRT and LT+Pbo (23% vs. 24%; p = 0.95). Total testosterone increased more in LT+TRT than LT+Pbo (133% vs. 32%; p = 0.005). Based on Next Generation Sequencing, of the 39 160 and 39 115 genes detected in LT+TRT and LT+Pbo, respectively, 195 were differentially expressed in LT+TRT and 158 in LT+Pbo. Gene Ontology enrichment analyses revealed that in LT+TRT, just four muscle-related pathways (muscle organ development, muscle organ morphogenesis, regulation of skeletal muscle contraction, muscle atrophy) were downregulated and one pathway (muscle system process) was upregulated. In contrast, in LT+Pbo, nine muscle-related pathways (muscle system process, muscle tissue development, muscle organ development, skeletal muscle tissue development, skeletal muscle organ development, skeletal muscle cell differentiation, muscle organ morphogenesis, response to stimuli involved in regulation of muscle adaptation, muscle atrophy) and one pathway related to bone (bone mineralization involved in bone maturation) were downregulated. Muscle system process was upregulated in LT+TRT but downregulated in LT+Pbo. RT-PCR analyses showed that LT+TRT resulted in a higher expression of MYOD1 (p = 0.02) and WNT4 (p = 0.02), key genes involved in muscle and bone metabolism, respectively, compared with LT+Pbo. We also observed significantly higher mRNA expression of MYBPH (p = 0.006), SCN3B (p = 0.02) and DSC2 (p = 0.01), genes involved in the muscle system process, in response to LT+TRT compared with LT+Pbo.

CONCLUSION

The addition of TRT to lifestyle therapy mitigates the weight-loss-induced reduction of muscle mass and BMD via countering the weight-loss-induced downregulation of genes involved in muscle and bone anabolism.

MiceDEGdb: a knowledge base on differentially expressed mouse genes as a model object in biomedical research

The fundamental understanding of many biological processes that unfold in a human body has become possible due to experimental studies on animal models. The backbone of modern biomedical research is the use of mouse models for studying important pathophysiological mechanisms, assessing new therapeutic approaches and making decisions on acceptance or rejection of new candidate medicines in preclinical trials. The use of mice is advantageous because they have small size, are easy to keep and to genetically modify. Mice make up more than 90 % of the rodents used for pharmaceutical research. We present the pilot version of MiceDEGdb, a knowledge base on the genes that are differentially expressed in the mouse used as a model object in biomedical research. MiceDEGdb is a collection of published data on gene expression in mouse strains used for studying age-related diseases, such as hypertension, periodontal disease, bone fragility, renal fibrosis, smooth muscle remodeling, heart failure and circadian rhythm disorder. The pilot release of MiceDEGdb contains 21,754 DEGs representing 9,769 unique Mus musculus genes the transcription levels whereof were found as being changed in 25 RNA-seq experiments involving eight tissues - gum, bone, kidney, right ventricle, aortic arch, hippocampus, skeletal muscle and uterus - in six genetic mouse strains (C57BL/6J, Ren1cCre|ZsGreen, B6.129S7(Cg)-Polgtm1Prol/J, BPN/3J, BPH/2J and Kunming) used as models of eight human diseases - all these data were based on information in 10 original articles. MiceDEGdb is novel in that it features a curated annotation of changes in the expression levels of mouse DEGs using independent biomedical publications about same-direction changes in the expression levels of human homologs in patients with one disease or the other. In its pilot release, MiceDEGdb documented 85,092 such annotations for 318 human genes in 895 diseases, as suggest to 912 scientific articles referenced by their PubMed ID. The information contained in MiceDEGdb may be of interest to geneticists, molecular biologists, bioinformatics scientists, clinicians, pharmacologists and genetic advisors in personalized medicine. MiceDEGdb is freely available at https://www.sysbio.ru/MiceDEGdb.

Unravelling the transcriptomic symphony of muscle ageing: key pathways and hub genes altered by ageing and caloric restriction in rat muscle revealed by RNA sequencing

Age-related muscle wasting, sarcopenia is an extensive loss of muscle mass and strength with age and 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 survey the global changes in protein-coding gene expression occurring in skeletal muscle with age. Caloric restriction (CR) is a known prophylactic intervention against sarcopenia. Therefore, total RNA was isolated from the muscle tissue of both rats fed ad libitum and CR rats. RNA-seq 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 immune responses; 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 highlights 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 potential future therapeutic interventions against sarcopenia.

Elucidation of anti-human melanoma and anti-aging mechanisms of compounds from green seaweed Caulerpa racemosa

Human melanoma is linked with aging-related disorders, prompting interest in the development of functional foods derived from natural ingredients to mitigate its incidence. Molecules in green seaweeds such as Caulerpa racemosa can serve this purpose due to their anti-tumor and anti-inflammatory properties. A previous work study compounds profiling has been carried out, and in this research the molecular docking studies targeting receptors associated with melanoma (GRP78, IRE1, BRAF) and aging (mTOR, AMPK, SIRT1) identified four promising compound in an extract of C. racemosa. The current study aims to the mechanism of those compounds at a cellular level using the human A375 (BRAF-V600E mutation) and A375 and B16-F10 cell lines. The MTT assay was used to evaluate the potential of GSCRE compounds against A375 and B16-F10 cell lines, with comparisons made to normal HDFa cell lines. Results indicated that compound C2, also known as Caulersin, demonstrated a significantly different ∆G affinity binding score compared to the control drug Dabrafenib. GSCRE crude extract, particularly C2, showed potential in modulating mTOR, AMPK, and SIRT1 pathways and downregulating GRP78, IRE1, and BRAF signaling (p < 0.05). Interestingly, C2 was less effective in suppressing A375 and B16-F10 cell lines (LD50 C2 < LD50 Dabrafenib/control), with its LD50 value nearly matching that of the Trametinib control in B16-F10 cell lines. Consequently, GSCRE, especially C2 or Caulersin, shows promise as a new molecule for developing functional foods to combat aging and human melanoma. However, further in vivo studies and clinical trials are necessary to confirm these findings.

Differentially Expressed Genes and Molecular Susceptibility to Human Age-Related Diseases

Mainstream transcriptome profiling of susceptibility versus resistance to age-related diseases (ARDs) is focused on differentially expressed genes (DEGs) specific to gender, age, and pathogeneses. This approach fits in well with predictive, preventive, personalized, participatory medicine and helps understand how, why, when, and what ARDs one can develop depending on their genetic background. Within this mainstream paradigm, we wanted to find out whether the known ARD-linked DEGs available in PubMed can reveal a molecular marker that will serve the purpose in anyone's any tissue at any time. We sequenced the periaqueductal gray (PAG) transcriptome of tame versus aggressive rats, identified rat-behavior-related DEGs, and compared them with their known homologous animal ARD-linked DEGs. This analysis yielded statistically significant correlations between behavior-related and ARD-susceptibility-related fold changes (log₂ values) in the expression of these DEG homologs. We found principal components, PC1 and PC2, corresponding to the half-sum and the half-difference of these log₂ values, respectively. With the DEGs linked to ARD susceptibility and ARD resistance in humans used as controls, we verified these principal components. This yielded only one statistically significant common molecular marker for ARDs: an excess of Fcγ receptor IIb suppressing immune cell hyperactivation.

Mitochondria transplant therapy improves regeneration and restoration of injured skeletal muscle

BACKGROUND

Injection of exogenous mitochondria has been shown to improve the ischaemia-damaged myocardium, but the effect of mitochondrial transplant therapy (MTT) to restore skeletal muscle mass and function has not been tested following neuromuscular injury. Therefore, we tested the hypothesis that MTT would improve the restoration of muscle function after injury.

METHODS

BaCl₂ was injected into the gastrocnemius muscle of one limb of 8-12-week-old C57BL/6 mice to induce damage without injury to the resident stem cells. The contralateral gastrocnemius muscle was injected with phosphate-buffered saline (PBS) and served as the non-injured intra-animal control. Mitochondria were isolated from donor mice. Donor mitochondria were suspended in PBS or PBS without mitochondria (sham treatment) and injected into the tail vein of BaCl₂ injured mice 24 h after the initial injury. Muscle repair was examined 7, 14 and 21 days after injury.

RESULTS

MTT did not increase systemic inflammation in mice. Muscle mass 7 days following injury was 21.9 ± 2.1% and 17.4 ± 1.9% lower (P < 0.05) in injured as compared with non-injured intra-animal control muscles in phosphate-buffered saline (PBS)- and MTT-treated animals, respectively. Maximal plantar flexor muscle force was significantly lower in injured as compared with uninjured muscles of PBS-treated (-43.4 ± 4.2%, P < 0.05) and MTT-treated mice (-47.7 ± 7.3%, P < 0.05), but the reduction in force was not different between the experimental groups. The percentage of collagen and other non-contractile tissue in histological muscle cross sections, was significantly greater in injured muscles of PBS-treated mice (33.2 ± 0.2%) compared with MTT-treated mice (26.5 ± 0.2%) 7 days after injury. Muscle wet weight and maximal muscle force from injured MTT-treated mice had recovered to control levels by 14 days after the injury. However, muscle mass and force had not improved in PBS-treated animals by 14 days after injury. The non-contractile composition of the gastrocnemius muscle tissue cross sections was not different between control, repaired PBS-treated and repaired MTT-treated mice 14 days after injury. By 21 days following injury, PBS-treated mice had fully restored gastrocnemius muscle mass of the injured muscle to that of the uninjured muscle, although maximal plantar flexion force was still 19.4 ± 3.7% (P < 0.05) lower in injured/repaired gastrocnemius as compared with uninjured intra-animal control muscles.

CONCLUSIONS

Our results suggest that systemic mitochondria delivery can enhance the rate of muscle regeneration and restoration of muscle function following injury.

Systematic Insight of Resveratrol Activated SIRT1 Interactome through Proximity Labeling Strategy

SIRT1 functions by regulating the modification of proteins or interacting with other proteins to form complexes. It has been widely studied and found to play significant roles in various biological processes and diseases. However, systematic studies on activated-SIRT1 interactions remain limited. Here, we present a comprehensive SIRT1 interactome under resveratrol stimulation through proximity labeling methods. Our results demonstrated that RanGap1 interacted with SIRT1 in HEK 293T cells and MCF-7 cells. SIRT1 regulated the protein level of RanGap1 and had no obvious effect on RanGap1 transcription. Moreover, the overexpression of Rangap1 increased the ROS level in MCF-7 cells, which sensitized cells to resveratrol and reduced the cell viability. These findings provide evidence that RanGap1 interacts with SIRT1 and influences intracellular ROS, critical signals for mitochondrial functions, cell proliferation and transcription. Additionally, we identified that the SIRT1-RanGap1 interaction affects downstream signals induced by ROS. Overall, our study provides an essential resource for future studies on the interactions of resveratrol-activated SIRT1. There are conflicts about the relationship between resveratrol and ROS in previous reports. However, our data identified the impact of the resveratrol-SIRT1-RanGap1 axis on intracellular ROS.

Ameliorating Inflammation in Insulin-resistant Rat Adipose Tissue with Abdominal Massage Regulates SIRT1/NF-κB Signaling

It was the aim of this study to determine whether abdominal massage reverses high-fat diet-induced insulin resistance compared with RSV treatment. A total of sixty male Sprague-Dawley rats were randomly placed in one of four groups:the non-fat diet (NFD), the high-fat diet (HFD), the HFD with abdominal massage (HFD+ AM), and the HFD plus resveratrol (HFD+ RSV). For eight weeks, rats were fed high-fat diets to create insulin resistance, followed by six weeks of either AM or RSV. Molecular mechanisms of adipogenesis and cytokine production in rats with high-fat diets were investigated. The model rat adipose tissue showed significant improvements in obesity, glucose intolerance, and the accumulation of lipid in the body [the total cholesterol level (TC), triglycerides (TG), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C)], metabolic effects of glucose [The fasting blood glucose (FBG), Fasting insulin levels (FINS)], inflammatory status [interleukin-6 (IL-6) and tumor necrosis factor (TNF)-α, C-reactive protein (CRP)], and macrophage polarization after AM or RSV treatment. Further, AM increased SIRT1/NF-κB signaling in rat adipose tissue. Accordingly, in rat adipose tissue, our results indicate that AM regulates the secretion of proinflammatory cytokines, blood sugar levels, and related signaling pathways, contributing to improvement of IR, which may serves as a new therapeutic approach for the treatment for IR.