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|116||IL-6 selectively stimulates fat metabolism in human skeletal muscle.|
Wolsk E; Mygind H; Grondahl TS; Pedersen BK; Hall GV
Am J Physiol Endocrinol Metab 2010; 299(5): E832-40
PubMed ID: 20823453
Interleukin (IL)-6 is chronically elevated in type 2 diabetes but also during exercise. However, the exact metabolic role, and hence the physiological significance, has not been elucidated. The objective of this study was to investigate the in vivo effect of rhIL-6 on human fat and glucose metabolism and signalling of both adipose tissue and skeletal muscle. Eight healthy post-absorptive males were infused with either rhIL-6 or saline for 4 hours eliciting IL-6 levels of ~40 and ~1 pg mL(-1), respectively. Systemic, skeletal muscle, and adipose tissue fat and glucose metabolism was assessed before, during, and 2 hours after cessation of the infusion. Glucose metabolism was unaffected by rhIL-6. In contrast, rhIL-6 increased systemic fatty acid oxidation ~2-fold after 60 min and it remained elevated even 2 hours after the infusion. The increase in oxidation was followed by an increase in systemic lipolysis. Adipose tissue lipolysis and fatty acid kinetics were unchanged with rhIL-6 compared to saline infusion. Conversely, rhIL-6 infusion caused an increase in skeletal muscle unidirectional fatty acid and glycerol release, indicative of an increase in lipolysis. The increased lipolysis in muscle could account for the systemic changes. Skeletal muscle signalling increased after 1 hour of rhIL-6 infusion, indicated by a 4-fold increase in p-STAT3/STAT3 ratio, whereas no changes in phosphorylated AMPK or ACC levels could be observed. Our findings suggest that an acute increase in IL-6 at a normo-physiological level selectively stimulates lipolysis in skeletal muscle whereas adipose tissue is unaffected.