title: Regulators of human white adipose browning: evidence for sympathetic control and sexual dimorphic responses to sprint interval training.
abstract: 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±113 vs. 295±80 pg/mL; P = 0.43; mean±SE), but was increased during hypoxia mediated sympathetic activation (368±135); this response was abrogated (P = 0.035) with clonidine (269±93). 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±78 vs. 251±36; P = 0.046) but did not affect FNDC5 (P = 0.79). Irisin was decreased in males (127±18 vs. 90±23 ng/mL; P = 0.045) and increased in females (139±14 vs. 170±18). 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.
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Rebecca L
authors.initials: RL
authors.lastname: Scalzo
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Garrett L
authors.initials: GL
authors.lastname: Peltonen
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Gregory R
authors.initials: GR
authors.lastname: Giordano
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Scott E
authors.initials: SE
authors.lastname: Binns
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Anna L
authors.initials: AL
authors.lastname: Klochak
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Hunter L R
authors.initials: HL
authors.lastname: Paris
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Melani M
authors.initials: MM
authors.lastname: Schweder
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Steve E
authors.initials: SE
authors.lastname: Szallar
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Lacey M
authors.initials: LM
authors.lastname: Wood
authors.affiliation: Heart Center of the Rockies, University of Colorado Health, Fort Collins, Colorado, United States of America.
authors.forename: Dennis G
authors.initials: DG
authors.lastname: Larson
authors.affiliation: Heart Center of the Rockies, University of Colorado Health, Fort Collins, Colorado, United States of America.
authors.forename: Gary J
authors.initials: GJ
authors.lastname: Luckasen
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Matthew S
authors.initials: MS
authors.lastname: Hickey
authors.affiliation: Department of Health and Exercise Science, Colorado State University, Fort Collins, Colorado, United States of America.
authors.forename: Christopher
authors.initials: C
authors.lastname: Bell
mesh_terms: D002001:Adipose Tissue, Brown / Q000502:physiology*; D052436:Adipose Tissue, White / Q000502:physiology*; D000328:Adult; D005260:Female; D005346:Fibroblast Growth Factors / Q000097:blood; D005353:Fibronectins / Q000097:blood*; D006801:Humans; D008297:Male; D064797:Physical Conditioning, Human; D012420:Running / Q000502:physiology*; D012727:Sex Characteristics; D013564:Sympathetic Nervous System; D055815:Young Adult
chemical_list: C577593:FNDC5 protein, human; D005353:Fibronectins; C414620:fibroblast growth factor 21; D005346:Fibroblast Growth Factors