Browsing by Author "Fox, Carlton D"

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    Acute and chronic effects of resistance training on skeletal muscle markers of mitochondrial remodeling in older adults
    (Physiological Reports, 2020-08) Mesquita, Paulo HC; Lamb, Donald A; Parry, Hailey A; Moore, Johnathon H; Smith, Morgan A; Vann, Christopher G; Osburn, Shelby C; Fox, Carlton D; Ruple, Bradley A; Huggins, Kevin W; Fruge, Andrew D; Young, Kaelin C; Kavazis, Andreas N; Roberts, Michael D
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    An intron variant of the GLI family zinc finger 3 (GLI3) gene differentiates resistance training-induced muscle fiber hypertrophy in younger men.
    (FASEB journal : official publication of the Federation of American Societies for Experimental Biology, 2021-05) Vann, Christopher G; Morton, Robert W; Mobley, Christopher B; Vechetti, Ivan J; Ferguson, Brian K; Haun, Cody T; Osburn, Shelby C; Sexton, Casey L; Fox, Carlton D; Romero, Matthew A; Roberson, Paul A; Oikawa, Sara Y; McGlory, Chris; Young, Kaelin C; McCarthy, John J; Phillips, Stuart M; Roberts, Michael D
    We examined the association between genotype and resistance training-induced changes (12 wk) in dual x-ray energy absorptiometry (DXA)-derived lean soft tissue mass (LSTM) as well as muscle fiber cross-sectional area (fCSA; vastus lateralis; n = 109; age = 22 ± 2 y, BMI = 24.7 ± 3.1 kg/m2 ). Over 315 000 genetic polymorphisms were interrogated from muscle using DNA microarrays. First, a targeted investigation was performed where single nucleotide polymorphisms (SNP) identified from a systematic literature review were related to changes in LSTM and fCSA. Next, genome-wide association (GWA) studies were performed to reveal associations between novel SNP targets with pre- to post-training change scores in mean fCSA and LSTM. Our targeted investigation revealed no genotype-by-time interactions for 12 common polymorphisms regarding the change in mean fCSA or change in LSTM. Our first GWA study indicated no SNP were associated with the change in LSTM. However, the second GWA study indicated two SNP exceeded the significance level with the change in mean fCSA (P = 6.9 × 10-7 for rs4675569, 1.7 × 10-6 for rs10263647). While the former target is not annotated (chr2:205936846 (GRCh38.p12)), the latter target (chr7:41971865 (GRCh38.p12)) is an intron variant of the GLI Family Zinc Finger 3 (GLI3) gene. Follow-up analyses indicated fCSA increases were greater in the T/C and C/C GLI3 genotypes than the T/T GLI3 genotype (P < .05). Data from the Auburn cohort also revealed participants with the T/C and C/C genotypes exhibited increases in satellite cell number with training (P < .05), whereas T/T participants did not. Additionally, those with the T/C and C/C genotypes achieved myonuclear addition in response to training (P < .05), whereas the T/T participants did not. In summary, this is the first GWA study to examine how polymorphisms associate with the change in hypertrophy measures following resistance training. Future studies are needed to determine if the GLI3 variant differentiates hypertrophic responses to resistance training given the potential link between this gene and satellite cell physiology.
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    Molecular Differences in Skeletal Muscle After 1 Week of Active vs. Passive Recovery From High-Volume Resistance Training
    (Journal of Strength and Conditioning Research, 2021-08) Vann, Christopher G; Haun, Cody T; Osburn, Shelby C; Romero, Matthew A; Roberson, Paul A; Mumford, Petey W; Mobley, C Brooks; Holmes, Hudson M; Fox, Carlton D; Young, Kaelin C; Roberts, Michael D
    Abstract Vann, CG, Haun, CT, Osburn, SC, Romero, MA, Roberson, PA, Mumford, PW, Mobley, CB, Holmes, HM, Fox, CD, Young, KC, and Roberts, MD. Molecular differences in skeletal muscle after 1 week of active vs. passive recovery from high-volume resistance training. J Strength Cond Res 35(8): 2102–2113, 2021—Numerous studies have evaluated how deloading after resistance training (RT) affects strength and power outcomes. However, the molecular adaptations that occur after deload periods remain understudied. Trained, college-aged men (n = 30) performed 6 weeks of whole-body RT starting at 10 sets of 10 repetitions per exercise per week and finishing at 32 sets of 10 repetitions per exercise per week. After this period, subjects performed either active (AR; n = 16) or passive recovery (PR; n = 14) for 1 week where AR completed ∼15% of the week 6 training volume and PR ceased training. Variables related to body composition and recovery examined before RT (PRE), after 6 weeks of RT (POST), and after the 1-week recovery period (DL). Vastus lateralis (VL) muscle biopsies and blood samples were collected at each timepoint, and various biochemical and histological assays were performed. Group × time interactions (p < 0.05) existed for skeletal muscle myosin heavy chain (MHC)-IIa mRNA (AR > PR at POST and DL) and 20S proteasome activity (post-hoc tests revealed no significance in groups over time). Time effects (P < 0.05) existed for total mood disturbance and serum creatine kinase and mechano growth factor mRNA (POST > PRE &D L), VL pressure to pain threshold and MHC-IIx mRNA (PRE&DL > POST), Atrogin-1 and MuRF-1 mRNA (PRE < POST < DL), MHC-I mRNA (PRE < POST & DL), myostatin mRNA (PRE & POST < DL), and mechanistic target of rapamycin (PRE > POST & DL). No interactions or time effects were observed for barbell squat velocity, various hormones, histological metrics, polyubiquitinated proteins, or phosphorylated/pan protein levels of 4E-BP1, p70S6k, and AMPK. One week of AR after a high-volume training block instigates marginal molecular differences in skeletal muscle relative to PR. From a practical standpoint, however, both paradigms elicited largely similar responses.
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    Muscle fiber hypertrophy in response to 6 weeks of high-volume resistance training in trained young men is largely attributed to sarcoplasmic hypertrophy
    (PLOS ONE) Haun, Cody T; Vann, Christopher G; Osburn, Shelby C; Mumford, Petey W; Roberson, Paul A; Romero, Matthew A; Fox, Carlton D; Johnson, Christopher A; Parry, Hailey A; Kavazis, Andreas N; Moon, Jordan R; Badisa, Veera LD; Mwashote, Benjamin M; Ibeanusi, Victor; Young, Kaelin C; Roberts, Michael D
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    Pre-training Skeletal Muscle Fiber Size and Predominant Fiber Type Best Predict Hypertrophic Responses to 6 Weeks of Resistance Training in Previously Trained Young Men
    (Frontiers in Physiology) Haun, Cody T; Vann, Christopher G; Mobley, C Brooks; Osburn, Shelby C; Mumford, Petey W; Roberson, Paul A; Romero, Matthew A; Fox, Carlton D; Parry, Hailey A; Kavazis, Andreas N; Moon, Jordan R; Young, Kaelin C; Roberts, Michael D
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    Resistance training increases muscle NAD+ and NADH concentrations as well as NAMPT protein levels and global sirtuin activity in middle-aged, overweight, untrained individuals
    (Aging, 2020-05-05) Lamb, Donald A; Moore, Johnathon H; Mesquita, Paulo Henrique Caldeira; Smith, Morgan A; Vann, Christopher G; Osburn, Shelby C; Fox, Carlton D; Lopez, Hector L; Ziegenfuss, Tim N; Huggins, Kevin W; Goodlett, Michael D; Fruge, Andrew D; Kavazis, Andreas N; Young, Kaelin C; Roberts, Michael D
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    Skeletal muscle LINE-1 ORF1 mRNA is higher in older humans but decreases with endurance exercise and is negatively associated with higher physical activity
    (Journal of Applied Physiology, 2019-10-01) Roberson, Paul A; Romero, Matthew A; Osburn, Shelby C; Mumford, Petey W; Vann, Christopher G; Fox, Carlton D; McCullough, Danielle J; Brown, Michael D; Roberts, Michael D
    The long interspersed nuclear element-1 (L1) is a retrotransposon that constitutes 17% of the human genome and is associated with various diseases and aging. Estimates suggest that ~100 L1 copies are capable of copying and pasting into other regions of the genome. Herein, we examined if skeletal muscle L1 markers are affected by aging or an acute bout of cycling exercise in humans. Apparently healthy younger (23 ± 3 y, n = 15) and older participants (58 ± 8 y, n = 15) donated a vastus lateralis biopsy before 1 h of cycling exercise (PRE) at ~70% of heart rate reserve. Second (2 h) and third (8 h) postexercise muscle biopsies were also obtained. L1 DNA and mRNA expression were quantified using three primer sets [5′ untranslated region (UTR), L1.3, and ORF1]. 5′UTR and L1.3 DNA methylation as well as ORF1 protein expression were also quantified. PRE 5′UTR, ORF1, or L1.3 DNA were not different between age groups ( P > 0.05). ORF1 mRNA was greater in older versus younger participants ( P = 0.014), and cycling lowered this marker at 2 h versus PRE ( P = 0.027). 5′UTR and L1.3 DNA methylation were higher in younger versus older participants ( P < 0.05). Accelerometry data collected during a 2-wk period before the exercise bout indicated higher moderate-to-vigorous physical activity (MVPA) levels per day was associated with lower PRE ORF1 mRNA in all participants ( r = −0.398, P = 0.032). In summary, skeletal muscle ORF1 mRNA is higher in older apparently healthy humans, which may be related to lower DNA methylation patterns. ORF1 mRNA is also reduced with endurance exercise and is negatively associated with higher daily MVPA levels. NEW & NOTEWORTHY The long interspersed nuclear element-1 (L1) gene is highly abundant in the genome and encodes for an autonomous retrotransposon, which is capable of copying and pasting itself into other portions of the genome. This is the first study in humans to demonstrate that certain aspects of skeletal muscle L1 activity are altered with aging. Additionally, this is the first study in humans to demonstrate that L1 ORF1 mRNA levels decrease after a bout of endurance exercise, regardless of age.
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    Skeletal Muscle Myofibrillar Protein Abundance Is Higher in Resistance-Trained Men, and Aging in the Absence of Training May Have an Opposite Effect
    (Sports) Vann, Christopher G; Roberson, Paul A; Osburn, Shelby C; Mumford, Petey W; Romero, Matthew A; Fox, Carlton D; Moore, Johnathon H; Haun, Cody; Beck, Darren T; Moon, Jordan R; Kavazis, Andreas N; Young, Kaelin C; Badisa, Veera LD; Mwashote, Benjamin M; Ibeanusi, Victor; Singh, Rakesh K; Roberts, Michael D
    Resistance training generally increases skeletal muscle hypertrophy, whereas aging is associated with a loss in muscle mass. Interestingly, select studies suggest that aging, as well as resistance training, may lead to a reduction in the abundance of skeletal muscle myofibrillar (or contractile) protein (per mg tissue). Proteomic interrogations have also demonstrated that aging, as well as weeks to months of resistance training, lead to appreciable alterations in the muscle proteome. Given this evidence, the purpose of this small pilot study was to examine total myofibrillar as well as total sarcoplasmic protein concentrations (per mg wet muscle) from the vastus lateralis muscle of males who were younger and resistance-trained (denoted as YT, n = 6, 25 ± 4 years old, 10 ± 3 self-reported years of training), younger and untrained (denoted as YU, n = 6, 21 ± 1 years old), and older and untrained (denoted as OU, n = 6, 62 ± 8 years old). The relative abundances of actin and myosin heavy chain (per mg tissue) were also examined using SDS-PAGE and Coomassie staining, and shotgun proteomics was used to interrogate the abundances of individual sarcoplasmic and myofibrillar proteins between cohorts. Whole-body fat-free mass (YT > YU = OU), VL thickness (YT > YU = OU), and leg extensor peak torque (YT > YU = OU) differed between groups (p < 0.05). Total myofibrillar protein concentrations were greater in YT versus OU (p = 0.005), but were not different between YT versus YU (p = 0.325). The abundances of actin and myosin heavy chain were greater in YT versus YU (p < 0.05) and OU (p < 0.001). Total sarcoplasmic protein concentrations were not different between groups. While proteomics indicated that marginal differences existed for individual myofibrillar and sarcoplasmic proteins between YT versus other groups, age-related differences were more prominent for myofibrillar proteins (YT = YU > OU, p < 0.05: 7 proteins; OU > YT = YU, p < 0.05: 11 proteins) and sarcoplasmic proteins (YT = YU > OU, p < 0.05: 8 proteins; OU > YT&YU, p < 0.05: 29 proteins). In summary, our data suggest that modest (~9%) myofibrillar protein packing (on a per mg muscle basis) was evident in the YT group. This study also provides further evidence to suggest that notable skeletal muscle proteome differences exist between younger and older humans. However, given that our n-sizes are low, these results only provide a preliminary phenotyping of the reported protein and proteomic variables.
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    Skeletal Muscle Protein Composition Adaptations to 10 Weeks of High-Load Resistance Training in Previously-Trained Males
    (Frontiers in Physiology) Vann, Christopher G; Osburn, Shelby C; Mumford, Petey W; Roberson, Paul A; Fox, Carlton D; Sexton, Casey L; Johnson, McLelland-Rae; Johnson, Joel S; Shake, Jacob; Moore, Johnathon H; Millevoi, Kevin; Beck, Darren T; Badisa, Veera LD; Mwashote, Benjamin M; Ibeanusi, Victor; Singh, Rakesh K; Roberts, Michael D
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    The effects of resistance training with or without peanut protein supplementation on skeletal muscle and strength adaptations in older individuals
    (Journal of the International Society of Sports Nutrition, 2020-01-03) Lamb, Donald A; Moore, Johnathon H; Smith, Morgan A; Vann, Christopher G; Osburn, Shelby C; Ruple, Bradley A; Fox, Carlton D; Smith, Kristen S; Altonji, Olivia M; Power, Zade M; Cerovsky, Annsley E; Ross, C Owen; Cao, Andy T; Goodlett, Michael D; Huggins, Kevin W; Fruge, Andrew D; Young, Kaelin C; Roberts, Michael D