Kyle L. Sunderland

Acute Loading and Aging Effects on Myostatin Pathway Biomarkers in Human Skeletal Muscle After Three Sequential Bouts of Resistance Exercise

To determine the influence of age and resistance exercise on myostatin pathway-related genes, younger (n = 10; 28 ± 5 years) and older (n = 10; 68 ± 6 years) men underwent four testing conditions (T1-T4). A baseline (T1) muscle sample was obtained, whereas the second and third biopsies were obtained 48 hours following the first and second training sessions (T2, T3), and a final biopsy was taken 24 hours following T3. The training sessions consisted of 3 sets of 10 repetitions (80% of one repetition maximum) on leg press, hack squat, and leg extension exercises. Follistatin (FST) messenger RNA was greater in older compared with younger men at T1 and T2 (p < .05). Follistatin-like 3 (FSTL3) messenger RNA was greater in older compared with younger men at T1 and T4 (p < .05). In older men, there was a significant decrease in myostatin (MSTN) messenger RNA at T4 (p < .05). Older men contained less active (Ser-425 phosphorylated) SMAD3 (p-SMAD3) protein than younger men at T3 and T4 (p < .05).Although it is well known that younger individuals possess a greater hypertrophic potential to resistance exercise, it appears that older individuals may paradoxically possess a more favorable resistance exercise response regarding myostatin pathway-related genes and a protein marker of pathway activity. Future research is warranted to examine the physiological significance of this age-dependent mechanism.

Oo2max and ventilatory threshold of trained cyclists are not affected by 28-day l-arginine supplementation

Sunderland, KL, Greer, F, and Morales, J. &OV0312;o2max and ventilatory threshold of trained cyclists are not affected by 28-day l-arginine supplementation. J Strength Cond Res 25(3): 833-837, 2011-The ergogenic effect of l-arginine on an endurance-trained population is not well studied. The few studies that have investigated l-arginine on this population have not been conducted in a laboratory setting or measured aerobic variables. The purpose of the current study is to determine if 28 days of l-arginine supplementation in trained male cyclists affects &OV0312;o2max and ventilatory threshold (VT). Eighteen (18) endurance-trained male cyclists (mean ± SD, age: 36.3±7.9 years; height: 182.4 ± 4.6 cm; and body mass: 79.5 ± 4.7 kg) performed a graded exercise test (GXT; 50 W + 25 W·min−1) before and after 28 days of supplementation with l-arginine (ARG; 2 × 6 g·d−1) or placebo (PLA; cornstarch). The GXT was conducted on the subjects own bicycle using the RacerMate CompuTrainer (Seattle, WA, USA). &OV0312;o2 was continuously recorded using the ParvoMedics TrueOne 2400 metabolic cart (Salt Lake City, UT, USA) and VT was established by plotting the ventilatory equivalent for O2 (&OV0312;E/&OV0312;o2) and the ventilatory equivalent for CO2 (&OV0312;E/&OV0312;co2) and identifying the point at which &OV0312;E/&OV0312;o2 increases with no substantial changes in &OV0312;E/&OV0312;co2. l-arginine supplementation had no effect from initial &OV0312;o2max (PL, 58.7 ± 7.1 ml·kg−1·min−1; ARG, 63.5 ± 7.3 ml·kg−1·min−1) to postsupplement &OV0312;o2max (PL, 58.9 ± 6.0 ml·kg−1·min−1; ARG, 63.2 ± 7.2 ml·kg−1·min−1). Also, no effect was seen from initial VT (PL, 75.7 ± 4.6% &OV0312;o2max; ARG, 76.0 ± 5.3% &OV0312;o2max) to postsupplement VT (PL, 74.3 ± 8.1% &OV0312;o2max; ARG, 74.2 ± 6.4% &OV0312;o2max). These results indicate that l-arginine does not impact &OV0312;o2max or VT in trained male cyclists.

The combined effects of exercise and ingestion of a meal replacement in conjunction with a weight loss supplement on body composition and fitness parameters in college-aged men and women.

Poole, CN, Roberts, MD, Dalbo, VJ, Tucker, PS, Sunderland, KL, DeBolt, ND, Billbe, BW, and Kerksick, CM. The combined effects of exercise and ingestion of a meal replacement in conjunction with a weight loss supplement on body composition and fitness parameters in college-aged men and women. J Strength Cond Res 25(1): 51-60, 2011-This study was performed to evaluate the combined effect of a meal replacement and an alleged weight loss supplement (WLS) on body composition, fitness parameters, and clinical health in moderately overweight college-aged men and women. Body mass, bench press 1 repetition maximum (1RM), leg press 1RM, body composition, &OV0312;O2max, fasting glucose (GLU), and lipid panels were evaluated before (T1) and after (T2) 8 weeks of combined resistance training (RT) and cardiovascular training (CVT). After T1, subjects were randomly assigned in a double-blind fashion to either the WLS (6 men, 7 women; 21 ± 5 years, 168 ± 8 cm, 75.4 ± 12.7 kg, 31.6 ± 7.7%BFAT) or placebo (PLA: 6 men, 6 women; 22 ± 4 years, 174 ± 9 cm, 84.1 ± 8.8 kg, 30.2 ± 5.6%BFAT) group. Both groups performed 3 d·wk−1 of combined progressive RT (2 × 12 reps of 8 exercises at 75-80% 1RM) and CVT (30 minutes on a cycle ergometer at 70-85% heart rate reserve). Subjects consumed 4 capsules per day and a once-daily meal replacement throughout the protocol. Percent body fat, bench press 1RM, and leg press 1RM significantly improved (p < 0.05) in both groups. Blood GLU (G × T; p = 0.048) improved in WLS and systolic blood pressure (SBP) approached significance (G × T; p = 0.06) in the WLS group. Follow-up analysis of SBP revealed a significant within-group decrease in the WLS group, whereas no within-group changes were found for either group for GLU. Practically speaking, daily supplementation with a meal replacement and a thrice weekly exercise program can increase fitness levels and improve body composition, whereas adding a thermogenic substance provides no additional benefit over fitness or body composition changes but may favorably alter serum markers of clinical health.

Leucine stimulates PPARβ/δ-dependent mitochondrial biogenesis and oxidative metabolism with enhanced GLUT4 content and glucose uptake in myotubes.

Leucine stimulates anabolic and catabolic processes in skeletal muscle, however little is known about the effects of leucine on peroxisome proliferator-activated receptor (PPAR) activity. This work characterized the effects of 24-h leucine treatment on metabolic parameters and protein expression in cultured myotubes. Leucine significantly increased PPARβ/δ expression as well as markers of mitochondrial biogenesis, leading to significantly increased mitochondrial content and oxidative metabolism in a PPARβ/δ-dependent manner. However, leucine-treated cells did not display significant alterations in uncoupling protein expression or oxygen consumed per relative mitochondrial content suggesting leucine-mediated increases in oxidative metabolism are a function of increased mitochondrial content and not altered mitochondrial efficiency. Leucine treatment also increased GLUT4 content and glucose uptake as well as PPARγ and FAS expression leading to increased total lipid content. Leucine appears to activate PPAR activity leading to increased mitochondrial biogenesis and elevated substrate oxidation, while simultaneously promoting substrate/lipid storage and protein synthesis.

Megalin and Androgen Receptor Gene Expression in Young and Old Human Skeletal Muscle Before and After Three Sequential Exercise Bouts

Poole, CN, Roberts, MD, Dalbo, VJ, Sunderland, KL, and Kerksick, CM. Megalin and androgen receptor gene expression in young and old human skeletal muscle before and after three sequential exercise bouts. J Strength Cond Res 25(2): 309-317, 2011-Androgen signaling occurs primarily via the androgen receptor. Megalin, a low-density lipoprotein endocytic receptor located in various mammalian tissues, has been recently shown to facilitate sex hormone-binding globulin (SHBG) steroid complexes across cell membranes. The purpose of this investigation is to determine if the megalin gene is expressed in human skeletal muscle and if present to determine how megalin and androgen receptor mRNA expression change in response to sequential exercise bouts with respect to aging. Ten younger (age: 18-25 years) and 10 older (age: 60-75 years) men completed 3 workouts (M, W, F) each consisting of 9 sets of lower-body exercises with 10 repetitions per set at 80% 1 repetition maximum. Vastus lateralis muscle biopsies were extracted at baseline (T1), 48 hours after workout 1 (T2) and 2 (T3), and 24 hours after workout 3 (T4), and blood samples were collected before and 5 minutes after each workout. Muscle was analyzed for megalin and androgen receptor expression using gene-specific primers and SYBR green chemistry, and blood was analyzed for serum testosterone, SHBG, and the free androgen index. Megalin was expressed in both young and old subjects across all time points, although no between- or within-group mean differences were detected at any time point. Androgen receptor was expressed higher in young men at all time points compared to in old men (p < 0.05), and a significant correlation (p < 0.05; r = 0.506) was found between serum testosterone and androgen receptor after workout 1. Based on our data, the gene coding for megalin is expressed inside skeletal muscle, but its role, if any, in steroid cellular transport cannot be determined. This finding could lay the groundwork for more mechanistic investigations to better delineate its functional role and its potential as a therapeutic adjunct for androgen-related disorders in healthy and aged populations.

Aging and Sequential Resistance Exercise Bout Effects on Housekeeping Gene Messenger RNA Expression in Human Skeletal Muscle

Abstract Sunderland, KL, Roberts, MD, Dalbo, VJ, and Kerksick, CM. Aging and sequential resistance exercise bout effects on housekeeping gene messenger RNA expression in human skeletal muscle. J Strength Cond Res 27(1): 1–7, 2013—The purpose of this study was to investigate how age and 1 week of conventional resistance exercise affects commonly used housekeeping gene (HKG) messenger RNAs (mRNAs) in skeletal muscle. Ten college-aged (18–25 years) and 10 older (60–76 years) men completed 3 lower-body resistance exercise bouts on Monday, Wednesday, and Friday, and muscle samples were obtained before bout 1 (T1), 48 hours after the first (T2) and second bouts (T3), and 24 hours after the third bout (T4). Raw Ct values indicated that &bgr;-actin and cyclophilin were more highly expressed in older vs. younger males (p < 0.01) at T1. When normalizing each HKG mRNA to the other 4 HKG mRNAs, CYC increased at T3 and glyceraldehyde-3-phosphate dehydrogenase decreased at T2 (p < 0.05) in younger men. This is one of the few studies to suggest that explicit HKG mRNAs should be used depending upon age group and resistance exercise intervention.

Characterization of the metabolic effect of β-alanine on markers of oxidative metabolism and mitochondrial biogenesis in skeletal muscle

[Purpose] β-alanine is a common component of numerous sports supplements purported to improve athletic performance through enhanced carnosine biosynthesis and related intracellular buffering. To date, the effects of β-alanine on oxidative metabolism remain largely unexplored. This work investigated the effects of β-alanine on the expression of proteins which regulate cellular energetics. [Methods] C2C12 myocytes were cultured and differentiated under standard conditions followed by treatment with either β-alanine or isonitrogenous non-metabolizable control D-alanine at 800μM for 24 hours. Metabolic gene and protein expression were quantified by qRT-PCR and immunoblotting, respectively. Glucose uptake and oxygen consumption were measured via fluorescence using commercially available kits. [Results] β-alanine-treated myotubes displayed significantly elevated markers of improved oxidative metabolism including elevated peroxisome proliferator-activated receptor β/δ (PPARβ/δ) and mitochondrial transcription factor a (TFAM) which led to increased mitochondrial content (evidenced by concurrent increases in cytochrome c content). Additionally, β-alanine-treated cells exhibited significantly increased oxygen consumption compared to control in a PPARβ/δ-dependent manner. β-alanine significantly enhanced expression of myocyte enhancer factor 2 (MEF-2) leading to increased glucose transporter 4 (GLUT4) content. [Conclusion] β-alanine appears to increase cellular oxygen consumption as well as the expression of several cellular proteins associated with improved oxidative metabolism, suggesting β-alanine supplementation may provide additional metabolic benefit (although these observations require in vivo experimental verification).

Electrophoretic separation of myosin heavy chain isoforms using a modified mini gel system.

Abstract Roberts, MD, Dalbo, VJ, Sunderland, KL, and Kerksick, CM. Electrophoretic separation of myosin heavy chain isoforms using a modified mini gel system. J Strength Cond Res 26(12): 3461–3468, 2012—The electrophoretic separation of myosin heavy chain isoforms from muscle biopsy homogenates has been widely practiced in the field of exercise physiology to examine how intrinsic (i.e., aging) and extrinsic (i.e., training) factors affect muscle phenotype. In the past, various research groups have used large and mini polyacrylamide gel systems to perform this delicate methodology. As technology has progressed, additional gel formats have been introduced, but available methodologies appear to be lacking. In this investigation, we successfully separated 3 distinct myosin heavy chain isoforms from various muscle samples using a modified mini gel system that can load up to 26 samples per gel. This article will outline our allocated protocol and discuss potential troubleshooting considerations for other researchers performing this intricate methodology. The outlined methodology has resulted in an ability to clearly resolute 3 distinct bands at molecular weights attributed to the myosin heavy chain isoforms in human skeletal muscle at a wide range of human ages (20–78 years). As additional technologies become available, the need to modify and adapt existing electrophoretic protocols for myosin heavy chain isoform separation and other protocols will continue to be evident.