IL-15 concentrations in skeletal muscle and subcutaneous adipose tissue in lean and obese humans: local effects of IL-15 on adipose tissue lipolysis.
Animal/cell investigations indicate that there is a decreased adipose tissue mass resulting from skeletal muscle (SkM) IL-15 secretion (e.g., SkM-blood-adipose tissue axis). IL-15 could regulate fat mass accumulation in obesity via lipolysis, although this has not been investigated in humans. Therefore, the purpose was to examine whether SkM and/or subcutaneous adipose tissue (SCAT) IL-15 concentrations were correlated with SCAT lipolysis in lean and obese humans and determine whether IL-15 perfusion could induce lipolysis in human SCAT. Local SkM and abdominal SCAT IL-15 (microdialysis) and circulating IL-15 (blood) were sampled in lean (BMI: 23.1 ± 1.9 kg/m(2); n = 10) and obese (BMI: 34.7 ± 3.5 kg/m(2); n = 10) subjects at rest/during 1-h cycling exercise. Lipolysis (SCAT interstitial glycerol concentration) was compared against local/systemic IL-15. An additional probe in SCAT was perfused with IL-15 to assess direct lipolytic responses. SkM IL-15 was not different between lean and obese subjects (P = 0.45), whereas SCAT IL-15 was higher in obese vs. lean subjects (P = 0.02) and was correlated with SCAT lipolysis (r = 0.45, P = 0.05). Exercise increased SCAT lipolysis in lean and obese (P < 0.01), but exercise-induced SCAT lipolysis changes were not correlated with exercise-induced SCAT IL-15 changes. Microdialysis perfusion resulting in physiological IL-15 concentrations in the adipose tissue interstitium increased lipolysis in lean (P = 0.04) but suppressed lipolysis in obese (P < 0.01). Although we found no support for a human IL-15 SkM-blood-adipose tissue axis, IL-15 may be produced in/act on the abdominal SCAT depot. The extent to which this autocrine/paracrine IL-15 action regulates human body composition remains unknown.
Human Performance Laboratory, East Carolina University, Greenville, North Carolina; Departments of Kinesiology and.
Joseph R
JR
Pierce
Human Performance Laboratory, East Carolina University, Greenville, North Carolina; Departments of Kinesiology and.
Jill M
JM
Maples
Human Performance Laboratory, East Carolina University, Greenville, North Carolina; Departments of Kinesiology and Physiology and Center for Health Disparities, East Carolina University, Greenville, North Carolina; and Discipline of Biokinetics, Exercise, and Leisure Sciences, School of Health Sciences, University of KwaZulu-Natal, Durban, South Africa Hicknerr@ecu.edu.
Robert C
RC
Hickner
D000273:Adipose Tissue / Q000187:drug effects* / Q000378:metabolism; D000293:Adolescent; D000328:Adult; D015444:Exercise / Q000502:physiology; D005260:Female; D006801:Humans; D019409:Interleukin-15 / Q000008:administration & dosage* / Q000032:analysis / Q000378:metabolism; D008066:Lipolysis / Q000187:drug effects*; D008297:Male; D017551:Microdialysis; D018482:Muscle, Skeletal / Q000187:drug effects* / Q000378:metabolism; D009765:Obesity / Q000097:blood / Q000378:metabolism*; D012146:Rest / Q000502:physiology; D050151:Subcutaneous Fat / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D013851:Thinness / Q000097:blood / Q000378:metabolism*; D055815:Young Adult
D019409:Interleukin-15
adipokine; adipose tissue metabolism; interleukin; microdialysis; myokine