Active muscle regeneration following eccentric contraction-induced injury is similar between healthy young and older adults

Abstract

Repair of skeletal muscle after injury is a key aspect of maintaining proper musculoskeletal function. Studies have suggested that regenerative processes, including myogenesis and angiogenesis, are impaired during advanced age, but evidence from humans is limited. This study aimed to compare active muscle regeneration between healthy young and older adults. We evaluated changes in clinical, biochemical, and immunohistochemical indices of muscle regeneration at precisely 2 (T2) and 7 (T3) days following acute muscle injury. Men and women, aged 18-30 and ≥70 years, matched for gender and body mass index, performed 150 unilateral, eccentric contractions of the plantar flexors at 110% of one repetition maximum. Data were analyzed using analysis of covariance, adjusted for gender, habitual physical activity, and baseline level of the outcome. A total of 30 young (n = 15; 22.5 ± 3.7 yr) and older (n = 15; 75.8 ± 5.0 yr) adults completed the study. Following muscle injury, force production declined 16% and 14% in young and older adults, respectively, by T2 and in each group, returned to 93% of baseline strength by T3. Despite modest differences in the pattern of response, postinjury changes in intramuscular concentrations of myogenic growth factors and number of myonuclear (4',6-diamidino-2-phenylindole+ and paired box 7+) cells were largely similar between groups. Likewise, postinjury changes in serum and intramuscular indices of inflammation (e.g., TNF-α and monocyte chemoattractant protein-1) and angiogenesis (e.g., VEGF and kinase insert domain receptor) did not differ significantly between groups. These findings suggest that declines in physical activity and increased co-morbidity may contribute to age-related impairments in active muscle regeneration rather than aging per se.

Intestinal Permeability Biomarker Zonulin is Elevated in Healthy Aging

“…Exclusion criteria designed to recruit healthy individuals free of chronic disease and other details of inclusion/exclusion criteria were previously published, and same cohort of subjects was also used in this study. 12 Strength of the plantar flexor muscles was evaluated based on methodology described previously. 12 To evaluate physical activity habits, participants wore validated physical activity monitor (SenseWear; BodyMedia, Pittsburgh, PA) for 7 days.…”

“…12 Strength of the plantar flexor muscles was evaluated based on methodology described previously. 12 To evaluate physical activity habits, participants wore validated physical activity monitor (SenseWear; BodyMedia, Pittsburgh, PA) for 7 days. 13 Fasting venous blood samples were drawn and serum was used to quantify TNF-α (Millipore), IL-6 (R & D Systems), HMGB1 (Antibodies online), and zonulin (Immundiagnostik AG).…”

Effects of a one-year physical activity program on serum C-terminal Agrin Fragment (CAF) concentrations among mobility-limited older adults

“…Linear regression models were created to evaluate the relationships between baseline CAF concentrations and longitudinal changes in CAF concentrations with changes in SPPB score and 400 m walking speed at 12 months. Regression models were created using the stepwise procedure as published previously (23, 24). Variables includes in the models include age, co-morbidity, baseline CAF concentrations, and change in CAF concentration at 12 months.…”

Effects of blood-flow restriction on biomarkers of myogenesis in response to resistance exercise

“…Muscle mRNA expression was determined using quantitative real-time polymerase chain reaction (Q-PCR) as previously described (Buford et al 2014). Primer sequences were designed using the Applied Biosystems (ABI) Primer Express 3.0 software and used to construct commercially-synthesized oligonucleotide sense and antisense primers (Integrated DNA Technologies, Coralville, IA) for GADPH (NCBI Accession:J02642), MyoD (NM_002478), Myf5 (NM_005593), c-Met (NM_001127500), and eMHC (NM_002470.2).…”