Project description:For additional details see Ebert et al, Identification and Small Molecule Inhibition of an ATF4-dependent Pathway to Age-related Skeletal Muscle Weakness and Atrophy. Weight-matched cohorts of 22-month-old male C57BL/6 mice were provided ad libitum access to standard chow (control) or standard chow supplemented with 0.27% ursolic acid (UA) or 0.05% tomatidine (TM) for 2 months. After the 2 month treatment period, quadriceps femoris muscles were harvested. mRNA levels in muscles harvested from ursolic acid or tomatidine fed mice were normalized to levels in muscles fed control diet.
Project description:Skeletal muscle atrophy is a devastating and defining feature of cancer cachexia that reduces quality of life, treatment tolerance, and survival, but cannot be prevented or reversed by current management strategies. Ursolic acid is a natural dietary compound that has been shown to inhibit atrophy-associated changes in skeletal muscle mRNA expression in rodents and dogs, leading to beneficial changes in skeletal muscle structure and function. We hypothesized that dietary supplementation with ursolic acid might help support skeletal muscle mass and function during cancer. To test this hypothesis, we investigated ursolic acid's effects in five in vivo mouse models of cancer cachexia that are driven by pancreatic, colon, and lung cancer cells of mouse and human origin. We found that dietary supplementation with ursolic acid has broad-spectrum effects towards cancer-induced skeletal muscle atrophy, significantly preserving muscle mass in all five cancer cachexia models. Ursolic acid's positive effects on muscle mass and muscle fiber size led to significant improvements in grip strength and muscle tetanic force, persisted in the presence of chemotherapy, and were not associated with discernable changes in food intake or tumor growth. Ursolic acid appeared to generate its beneficial effects in skeletal muscle by acting directly on muscle cells, inhibiting catabolic effects of tumor-derived secreted factors, and inhibiting > 90% of cancer-induced changes in skeletal muscle mRNA expression. These results strongly nominate ursolic acid as a promising potential nutritional approach for supporting muscle mass and function in individuals with cancer.
Project description:We assessed donor-specific response to tomatidine known to inhibit muscle atrophy and promote skeletal muscle hypertrophy. Bioinformatic analyses revealed that infusion of tomatidine during electrical stimulation modulated the IL-6/JAK/STAT3 pathway improving muscle synchronicity in young myobundles compared to those from older volunteers.
Project description:Heterochronic blood exchange (HBE) has demonstrated that circulating factors restore youthful features to aged tissues. However, the systemic mediators of those rejuvenating effects remain poorly defined. We show that the beneficial effect of young blood on aged muscle regeneration was diminished when serum was depleted of extracellular vesicles (EVs). Whereas EVs from young animals rejuvenate aged cell bioenergetics and skeletal muscle regeneration, aging shifts EV subpopulation heterogeneity and compromises downstream benefits on recipient cells. Machine learning classifiers revealed that aging shifts the nucleic acid, but not protein, fingerprint of circulating EVs. Alterations in sub-population heterogeneity were accompanied by declines in transcript levels of the pro-longevity protein, α-Klotho, and injection of EVs improved muscle regeneration in a Klotho mRNA-dependent manner. These studies demonstrate that EVs play a key role in the rejuvenating effects of HBE and that Klotho transcripts within EVs phenocopy the effects of young serum on aged skeletal muscle.
Project description:Aging is a major international concern and brings with it formidable socioeconomical and healthcare challenges. An attainable approach to improve general health in humans is using small molecules. Tomatidine, a natural compound abundant in unripe tomatoes, inhibits aging-related skeletal muscle atrophy in mice. Here we show that tomatidine extends lifespan and healthspan in the aging animal model C. elegans, which shares many major longevity pathways with those of mammals. Tomatidine improves behaviors related to healthspan, including increased pharyngeal pumping and swimming movement, and also reduces deterioration of muscle cells in worms. Microarray, imaging, and behavioral analysis reveal that tomatidine maintains mitochondrial homeostasis through mitochondrial biogenesis and PINK-1/DCT-1-dependent mitophagy. Mechanistically, tomatidine induces mitochondrial hormesis by mildly inducing ROS production, which in turn activates the cellular antioxidant response SKN-1/Nrf2 pathway, followed by increased mitophagy in worms, primary rat neurons, and human cells. Our data suggest that tomatidine may delay some physiological aspects of aging, and points to new approaches for pharmacological interventions towards diseases of aging.
Project description:Arrestin Domain Containing 2 and 3 (Arrdc2/3) are genes whose mRNA contents are decreased in young skeletal muscle following mechanical overload. Arrdc3 is linked to the regulation of signaling pathways in non-muscle cells that could influence skeletal muscle size. Despite a similar amino acid sequence, Arrdc2 function remains undefined. The purpose of this study was to further explore the relationship of Arrdc2/Arrdc3 expression with changes in mechanical load in young and aged muscle and define the effect of Arrdc2/3 expression on myotube diameter. In young and aged mice, mechanical load was decreased using hindlimb suspension while mechanical load was increased by reloading previously unloaded muscle or inducing high force contractions. Arrdc2 and Arrdc3 mRNAs were overexpressed in C2C12 myotubes using adenoviruses. Myotube diameter was determined 48 h post-transfection and RNA sequencing was performed on those samples. Arrdc2 and Arrdc3 mRNA content was higher in the unloaded muscle within 1 day of disuse and remained higher up through 10 days. The induction of Arrdc2 mRNA was more pronounced in aged muscle than young muscle in response to unloading. Reloading previously unloaded muscle of young and aged mice restored Arrdc2 and Arrdc3 levels to ambulatory levels. Increasing mechanical load beyond normal ambulatory levels lowered Arrdc2 but not Arrdc3 mRNA in young and aged muscle. Arrdc2, not Arrdc3, overexpression was sufficient to lower myotube diameter in C2C12 cells in part by altering the transcriptome favoring muscle atrophy. These data are consistent with Arrdc2 contributing to disuse atrophy, particularly in aged muscle.