title: The potential role of irisin in the thermoregulatory responses to mild cold exposure in adults.
abstract: To determine the acute effect of a mild cold exposure on thermoregulatory thermogenesis and the role of circulating irisin in the process.
  
  
  
  We studied 22 adults (9 males, 13 females) aged 57.7 ± 10.07 years and body mass index 27.8 ± 4.52 kg/m(2) . Participants experienced a 90-min exposure to 20°C and 25°C in a randomized cross-over design. Resting metabolic rate (RMR), forearm to finger-tip gradient (FFG), blood pressure (BP), in-the-ear temperature (IET), and fasting bloods were measured on each occasion.
  
  
  
  There were significant increases in FFG [mean ± SD: +3.8 ± 3.0°C, P < 0.001], systolic blood pressure (SBP) [+8 ± 13 mm Hg, P = 0.015], and diastolic blood pressure (DBP) [+4 ± 6 mm Hg, P = 0.005] and decreases in IET [-0.24 ± 0.29°C, P = 0.001]. Overall, RMR [+190 ± 570 kJ/d, P = 0.135], irisin, glucose or insulin did not differ between temperatures. There were no significant between-gender differences, but males significantly increased SBP (+12 ± 16, P = 0.02) and DBP (+6 ± 7, P = 0.02) with decreases in heart rate (-4 ± 3, P = 0.002), while females did not. Moreover men had approximately 50% higher thermogenic response while women had approximately 25% greater vasoconstrictor response. Adjusted for age, gender, insulin sensitivity, and body composition, fold changes in irisin were inversely related to respiratory quotient (r= -0.54, P = 0.048), while IET was related to FFG (r= -0.55, P = 0.043).
  
  
  
  Mild cold exposure increased vasoconstriction with a drop in IET and these were related. Greater irisin was related to a greater fasting fat oxidation in the absence of shivering. A potential gender bias in thermoregulation was noted. Am. J. Hum. Biol. 28:699-704, 2016. © 2016 Wiley Periodicals, Inc.
authors.affiliation: Health Promotion & Disease Prevention, School of Public Health, CHIRI-Metabolic Health, Curtin University, Perth, Western Australia, Australia.
authors.forename: Emily K
authors.initials: EK
authors.lastname: Calton
authors.affiliation: Health Promotion & Disease Prevention, School of Public Health, CHIRI-Metabolic Health, Curtin University, Perth, Western Australia, Australia. m.soares@curtin.edu.au.
authors.forename: Mario J
authors.initials: MJ
authors.lastname: Soares
authors.affiliation: Health Promotion & Disease Prevention, School of Public Health, CHIRI-Metabolic Health, Curtin University, Perth, Western Australia, Australia.
authors.forename: Anthony P
authors.initials: AP
authors.lastname: James
authors.affiliation: Faculty of Medicine, Flinders Centre for Epidemiology and Biostatistics School of Medicine, Nursing and Health Sciences, Flinders University of South Australia, Adelaide, South Australia, 5001.
authors.forename: Richard J
authors.initials: RJ
authors.lastname: Woodman
mesh_terms: D000328:Adult; D000368:Aged; D001315:Australia; D001481:Basal Metabolism; D001794:Blood Pressure; D001831:Body Temperature; D003080:Cold Temperature; D018592:Cross-Over Studies; D005215:Fasting / Q000097:blood; D005260:Female; D005353:Fibronectins / Q000378:metabolism*; D006801:Humans; D008297:Male; D008875:Middle Aged; D022722:Thermogenesis / Q000235:genetics / Q000502:physiology*
chemical_list: C577593:FNDC5 protein, human; D005353:Fibronectins