title: Passive heat loading links lipolysis and regulation of fibroblast growth factor-21 in humans.
abstract: There is relativley little information on the serum biomarkers of heat stress. Therefore, the goal of this study was to verify the effect of passive heat loading (PHL) on the expression of fibroblast growth factor-21 (FGF21) and free fatty acids (FFAs). Four PHL protocols based on intensity (39 °C vs. 43 °C, leg immersion, 30 min) and type (leg vs. half immersion, 42 °C, 30 min) were used. Each protocol was applied on a 2 day cycle to 12 healthy adult males (age, 22.4 ± 2.9 years; height, 174.1 ± 4.6 cm; weight, 71.3 ± 5.6 kg; body mass index, 23.1 ± 3.0). The subjects were categorized into two groups according to the study design (randomized, with a parallel trial). Body temperature, FGF21 and FFAs were determined prior to PH L, immediately and 60 min after PHL. Body temperature was significant higher (43 °C) than the 39 °C measured under identical PHL type (leg immersion). PHL was effective for the expression of FGF21 and for lipolysis. The quantitative levels of FGF21 and FFA increased with increasing temperature (39 °C<42 °C<43 °C). A significant difference in the quantitative levels of FGF21 and FFAs was also evident based on the type of PHL (leg<half immersion) even when PHL was applied at the same temperature (42 °C). In conclusion, PHL was effective for expressing FGF21 and for lipolysis. Therefore, PHL may be expected to help in the reduction of body fat. Additionally, when the identical type (leg immersion) of PHL is applied, a loading temperature of 43 °C is more effective for expressing FGF21 and for lipolysis than temperatures of 39 °C and 42 °C, and half immersion is more effective than leg immersion at 42 °C.
authors.affiliation: Department of Physiology, College of Medicine, Soonchunhyang University, 366-1 Ssangyong-dong, Cheonan 331-946, Republic of Korea.
authors.forename: Jeong-Beom
authors.initials: JB
authors.lastname: Lee
authors.affiliation: Department of Health Care, Graduate School, Soonchunhyang University, 646 Eupnae-ri, Shinchang-myeon, Asan 336-745, Republic of Korea. Electronic address: kimtw@sch.ac.kr.
authors.forename: Tae-Wook
authors.initials: TW
authors.lastname: Kim
mesh_terms: D000328:Adult; D001831:Body Temperature; D005230:Fatty Acids, Nonesterified / Q000097:blood; D005346:Fibroblast Growth Factors / Q000097:blood*; D018869:Heat-Shock Response; D006358:Hot Temperature; D006801:Humans; D007101:Immersion; D008066:Lipolysis; D008297:Male; D014867:Water
chemical_list: D005230:Fatty Acids, Nonesterified; C414620:fibroblast growth factor 21; D014867:Water; D005346:Fibroblast Growth Factors
keywords: FGF21; Half immersion; Leg immersion; Lipolysis; Passive heat loading