ObjectiveThe inappropriate release of free fatty acids from obese adipose tissue stores has detrimental effects on metabolism, but key molecular mechanisms controlling FFA release from adipocytes remain undefined. Although obesity promotes systemic inflammation, we find activation of the inflammation-associated Mitogen Activated Protein kinase ERK occurs specifically in adipose tissues of obese mice, and provide evidence that adipocyte ERK activation may explain exaggerated adipose tissue lipolysis observed in obesity.Methods and ResultsWe provide genetic and pharmacological evidence that inhibition of the MEK/ERK pathway in human adipose tissue, mice, and flies all effectively limit adipocyte lipolysis. In complementary findings, we show that genetic and obesity-mediated activation of ERK enhances lipolysis, whereas adipose tissue specific knock-out of ERK2, the exclusive ERK1/2 protein in adipocytes, dramatically impairs lipolysis in explanted mouse adipose tissue. In addition, acute inhibition of MEK/ERK signaling also decreases lipolysis in adipose tissue and improves insulin sensitivity in obese mice. Mice with decreased rates of adipose tissue lipolysis in vivo caused by either MEK or ATGL pharmacological inhibition were unable to liberate sufficient White Adipose Tissue (WAT) energy stores to fuel thermogenesis from brown fat during a cold temperature challenge. To identify a molecular mechanism controlling these actions, we performed unbiased phosphoproteomic analysis of obese adipose tissue at different time points following acute pharmacological MEK/ERK inhibition. MEK/ERK inhibition decreased levels of adrenergic signaling and caused de-phosphorylation of the β3-adrenergic receptor (β3AR) on serine 247. To define the functional implications of this phosphorylation, we showed that CRISPR/Cas9 engineered cells expressing wild type β3AR exhibited β3AR phosphorylation by ERK2 and enhanced lipolysis, but this was not seen when serine 247 of β3AR was mutated to alanine.ConclusionTaken together, these data suggest that ERK activation in adipocytes and subsequent phosphorylation of the β3AR on S247 are critical regulatory steps in the enhanced adipocyte lipolysis of obesity.
Kershner, AL, Fry, AC, and Cabarkapa, D. Effect of internal vs. external focus of attention instructions on countermovement jump variables in NCAA Division I student-athletes. J Strength Cond Res XX(X): 000–000, 2019—The purpose of this study was compare the effect of internal and external focus of attention instructions on force-time characteristics of the countermovement jump (CMJ) in collegiate student-athletes. Forty-three resistance-trained men ( JOURNAL/jscr/04.03/00124278-201906000-00002/inline-formula1/v/2023-08-19T002820Z/r/image-tiff ± SD; age = 20 ± 1.5 years) on an NCAA Division I baseball team volunteered to participate in this study. Each participant performed a total of 16 CMJs on a force platform while holding a wooden dowel on their shoulders to eliminate arm swing. Force and power parameters such as jump height (JH), peak velocity (PV), and mean concentric velocity (MCV) were calculated from force-time and position data. Paired-sample t-tests and Cohen's d effect sizes were used to examine differences between conditions. When subjects were instructed using an external focus, they demonstrated significantly (p < 0.05) greater JH, PV, and MCV compared with jumps performed with the internal focus (external JH = 48.0 ± 5.6 cm, internal JH = 46.4 ± 5.4 cm; external PV = 3.6 ± 0.3 m·s−1, internal PV = 3.5 ± 0.3 m·s−1; and external MCV = 2.31 ± 0.22 m·s−1, internal MCV = 2.25 ± 0.23 m·s−1). It is interesting to note that there was superior recall of the internal instructions during the manipulation checks that may suggest that the subjects consciously processed these instructions to a greater extent and reduced internal condition performance. These results indicate that instructions can alter the efficiency and performance of a skill. According to the literature and this study, if an optimum performance metric is desired, external focus of attention instructions should be used.
The purpose of the present study was (i) to explore the reliability of the most commonly used countermovement jump (CMJ) metrics, and (ii) to reduce a large pool of metrics with acceptable levels of reliability via principal component analysis to the significant factors capable of providing distinctive aspects of CMJ performance. Seventy-nine physically active participants (thirty-seven females and forty-two males) performed three maximal CMJs while standing on a force platform. Each participant visited the laboratory on two occasions, separated by 24–48 h. The most reliable variables were performance variables (CV = 4.2–11.1%), followed by kinetic variables (CV = 1.6–93.4%), and finally kinematic variables (CV = 1.9–37.4%). From the 45 CMJ computed metrics, only 24 demonstrated acceptable levels of reliability (CV ≤ 10%). These variables were included in the principal component analysis and loaded a total of four factors, explaining 91% of the CMJ variance: performance component (variables responsible for overall jump performance), eccentric component (variables related to the breaking phase), concentric component (variables related to the upward phase), and jump strategy component (variables influencing the jumping style). Overall, the findings revealed important implications for sports scientists and practitioners regarding the CMJ-derived metrics that should be considered to gain a comprehensive insight into the biomechanical parameters related to CMJ performance.
The purpose of the present study was to examine differences in game-related statistical parameters between National Basketball Association (NBA) regular and post-season competitive periods and to determine which variables have the greatest contribution in discriminating between winning and losing game outcomes. The data scraping technique was used to obtain publicly available NBA game-related statistics over a three-year span (2016–2019). The total number of games examined in the present investigation was 3933 (3690 regular season and 243 post-season games). Despite small to moderate effect sizes, the findings suggest that NBA teams’ style of play (i.e., tactical strategies) changes when transitioning from the regular to post-season competitive period. It becomes more conservative (i.e., fewer field goal attempts, assists, steals, turnovers, and points scored), most likely due to greater defensive pressure. Discriminant function analysis correctly classified winning and losing game outcomes during the regular and post-season competitive periods in 82.8% and 87.2% of cases, respectively. Two key game-related statistics capable of discriminating between winning and losing game outcomes were field goal percentage and defensive rebounding, accounting for 13.6% and 14.2% of the total percentage of explained variance during the regular season and 11.5% and 14.7% during post-season competitive periods. Also, overall shooting efficiency (i.e., free-throw, 2-point, and 3-point combined) accounted for 23–26% of the total percentage of explained variance.
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