Effects of PGC-1αoverexpression on the myogenic response during skeletal muscle regeneration

The ability of skeletal muscle to regenerate from injury is crucial for locomotion,metabolic health,and quality of life.Peroxisome proliferator-activated receptor-γcoactivator-1α(PGC1A)is a transcriptional coactivator required for mitochondrial biogenesis.Increased mitochondrial biogenesis is associated with improved muscle cell differentiation,however PGC1A's role in skeletal muscle regeneration following damage requires further investigation.The purpose of this study was to investigate the role of skeletal muscle-specific PGC1A overexpression during regeneration following damage.22 C57BL/6J(WT)and 26 PGC1A muscle transgenic(A1)mice were injected with either phosphate-buffered saline(PBS,uninjured control)or Bupivacaine(MAR,injured)into their tibialis anterior(TA)muscle to induce skeletal muscle damage.TA muscles were extracted 3-or 28-days postinjury and analyzed for markers of regenerative myogenesis and protein turnover.Pgc1a mRNA was~10–20 fold greater in A1 mice.Markers of protein synthesis,AKT and 4EBP1,displayed decreases in A1 mice compared to WT at both timepoints indicating a decreased protein synthetic response.Myod mRNA was~75%lower compared to WT 3 days post-injection.WT mice exhibited decreased cross-sectional area of the TA muscle at 28 days post-injection with bupivacaine compared to all other groups.PGC1A overexpression modifies the myogenic response during regeneration.

Development and progression of cancer cachexia:Perspectives from bench to bedside

Cancer cachexia(CC)is a devastating syndrome characterized by weight loss,reduced fat mass and muscle mass that affects approximately 80%of cancer patients and is responsible for 22%-30%of cancer-associated deaths.Understanding underlying mechanisms for the development of CC are crucial to advance therapies to treat CC and improve cancer outcomes.CC is a multi-organ syndrome that results in extensive skeletal muscle and adipose tissue wasting;however,CC can impair other organs such as the liver,heart,brain,and bone as well.A considerable amount of CC research focuses on changes that occur within the muscle,but cancer-related impairments in other organ systems are understudied.Furthermore,metabolic changes in organ systems other than muscle may contribute to CC.Therefore,the purpose of this review is to address degenerative mechanisms which occur during CC from a whole-body perspective.Outlining the information known about metabolic changes that occur in response to cancer is necessary to develop and enhance therapies to treat CC.As much of the current evidences in CC are from pre-clinical models we should note the majority of the data reviewed here are from preclinical models.

Neither autophagy nor exercise training mode affect exercise-induced beneficial adaptations in high fat-fed mice

Exercise mitigates obesity-associated pathologies;however,there is controversy regarding optimal exercise interventions.Autophagy,is known to decrease during obesity and is an important moderator for exercise adaptations.Purpose:To investigate individual and combined effects of different exercise interventions and autophagy inhibition on exercise adaptations during obesity.Methods:C57BL/6J mice initiated 45%high fat diet at 8 weeks of age.After 6 weeks of diet,animals were divided into moderate(MOD)or high intensity interval training interventions(HIIT),animals were further divided into autophagy inhibition or vehicle conditions(n=10/group).Animals exercised and autophagy was inhibited 3X/week by NSC185058 injections,thereby blocking autophagosome formation.Interventions continued for 4 weeks.Results:High fat diet impaired glucose handling~17%;exercise interventions normalized glucoregulation to prehigh fat diet levels,without differences between any interventions.High fat diet induced~25%decrease in aerobic capacity,which returned to baseline after exercise interventions,with no differences between any interventions.No effects of autophagy inhibition were noted.Conclusions:HIIT and MOD training confer similar health-related adaptations.

The effect of diet-induced obesity on extracellular matrix remodeling during skeletal muscle regeneration

Diet-induced obesity has previously been shown to occur with the concomitant rise in the expression of proin-flammatory cytokines and increases in collagen deposition.While it has been known that the regenerative process of skeletal muscle is altered in obese mice following an acute muscle injury,we sought to examine differences in the expression of various markers of extracellular matrix remodeling and repair.Our laboratory has previously reported an impaired inflammatory and protein synthetic signaling in these mice that may contribute negatively to the muscle regenerative process.To expand upon this previous investigation,tissues from these animals un-derwent further analysis to determine the extent of changes to the regenerative response within the extracellular matrix,including transcriptional changes in CollagenⅠ,CollagenⅢ,and Fibronectin.Here,we show that the expression of CollagenⅢ:Ⅰis significantly increased at 3-days post-injury in obese injured animals compared to lean injured animals(p=0.0338),and by 28-days the obese injured animals exhibit a significantly lower CollagenⅢ:Ⅰthan their lean injured counterparts(p=0.0035).We demonstrate an impaired response to an acute muscle injury in obese mice when compared with lean counterparts.However,further studies are required to elucidate translational consequences of these changes,as well as to determine any causative mechanisms that may be driving this effect.