%0 Journal Article
%T Regulators of Human White Adipose Browning: Evidence for Sympathetic Control and Sexual Dimorphic Responses to Sprint Interval Training
%A Rebecca L. Scalzo
%A Garrett L. Peltonen
%A Gregory R. Giordano
%A Scott E. Binns
%A Anna L. Klochak
%A Hunter L. R. Paris
%A Melani M. Schweder
%A Steve E. Szallar
%A Lacey M. Wood
%A Dennis G. Larson
%A Gary J. Luckasen
%A Matthew S. Hickey
%A Christopher Bell
%J PLOS ONE
%D 2014
%I Public Library of Science (PLoS)
%R 10.1371/journal.pone.0090696
%X The conversion of white adipose to the highly thermogenic beige adipose tissue has been proposed as a potential strategy to counter the unfavorable consequences of obesity. Three regulators of this conversion have recently emerged but information regarding their control is limited, and contradictory. We present two studies examining the control of these regulators. Study 1: In 10 young men, the plasma concentrations of irisin and fibroblast growth factor 21 (FGF21) were determined prior to and during activation of the sympathetic nervous system via hypoxic gas breathing (FIO2 = 0.11). The measurements were performed twice, once with and once without prior/concurrent sympathetic inhibition via transdermal clonidine administration. FGF21 was unaffected by basal sympathetic inhibition (338¡À113 vs. 295¡À80 pg/mL; P = 0.43; mean¡ÀSE), but was increased during hypoxia mediated sympathetic activation (368¡À135); this response was abrogated (P = 0.035) with clonidine (269¡À93). Irisin was unaffected by sympathetic inhibition and/or hypoxia (P>0.21). Study 2: The plasma concentration of irisin and FGF21, and the skeletal muscle protein content of fibronectin type III domain containing 5 (FNDC5) was determined in 19 young adults prior to and following three weeks of sprint interval training (SIT). SIT decreased FGF21 (338¡À78 vs. 251¡À36; P = 0.046) but did not affect FNDC5 (P = 0.79). Irisin was decreased in males (127¡À18 vs. 90¡À23 ng/mL; P = 0.045) and increased in females (139¡À14 vs. 170¡À18). Collectively, these data suggest a potential regulatory role of acute sympathetic activation pertaining to the browning of white adipose; further, there appears to be a sexual dimorphic response of irisin to SIT.
%U http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0090696