title: Reduced stress- and cold-induced increase in energy expenditure in interleukin-6-deficient mice.
abstract: Interleukin-6 (IL-6) deficient (-/-) mice develop mature onset obesity. Pharmacological studies have shown that IL-6 has direct lipolytic effects and when administered centrally increases sympathetic outflow. However, the metabolic functions of endogenous IL-6 are not fully elucidated. We aimed to investigate the effect of IL-6 deficiency with respect to cold exposure and cage-switch stress, that is, situations that normally increase sympathetic outflow. Energy metabolism, core temperature, heart rate, and activity were investigated in young preobese IL-6-/- mice by indirect calorimetry together with telemetry. Baseline measurements and the effect of cage-switch stress were investigated at thermoneutrality (30 degrees C) and at room temperature (20 degrees C). The effect of cold exposure was investigated at 4 degrees C. At 30 degrees C, the basal core temperature was 0.6 +/- 0.24 degrees C lower in IL-6-/- compared with wild-type mice, whereas the oxygen consumption did not differ significantly. The respiratory exchange ratio at 20 degrees C was significantly higher and the calculated fat utilization rate was lower in IL-6-/- mice. In response to cage-switch stress, the increase in oxygen consumption at both 30 and 20 degrees C was lower in IL-6-/- than in wild-type mice. The increase in heart rate was lower in IL-6-/- mice at 30 degrees C. At 4 degrees C, both the oxygen consumption and core temperature were lower in IL-6-/- compared with wild-type mice, suggesting a lower cold-induced thermogenesis in IL-6-/- mice. The present results indicate that endogenous IL-6 is of importance for stress- and cold-induced energy expenditure in mice.
authors.affiliation: Research Centre for Endocrinology and Metabolism, Sahlgrenska University Hospital, Gothenburg, Sweden. Ingrid.Wernstedt@medic.gu.se
authors.forename: Ingrid
authors.initials: I
authors.lastname: Wernstedt
authors.forename: Amanda
authors.initials: A
authors.lastname: Edgley
authors.forename: Anna
authors.initials: A
authors.lastname: Berndtsson
authors.forename: Jenny
authors.initials: J
authors.lastname: Fäldt
authors.forename: Göran
authors.initials: G
authors.lastname: Bergström
authors.forename: Ville
authors.initials: V
authors.lastname: Wallenius
authors.forename: John-Olov
authors.initials: JO
authors.lastname: Jansson
mesh_terms: D000818:Animals; D003080:Cold Temperature; D004734:Energy Metabolism / Q000235:genetics / Q000502:physiology*; D005260:Female; D015850:Interleukin-6 / Q000172:deficiency* / Q000235:genetics / Q000378:metabolism*; D008297:Male; D051379:Mice; D018345:Mice, Knockout; D009638:Norepinephrine / Q000097:blood; D013312:Stress, Physiological / Q000503:physiopathology*; D022722:Thermogenesis / Q000502:physiology
chemical_list: D015850:Interleukin-6; D009638:Norepinephrine