Interleukin-6 in combination with the interleukin-6 receptor stimulates glucose uptake in resting human skeletal muscle independently of insulin action.
Level 5 - mechanism / opinion, no new human data
Ex vivo human tissue bench research (mechanism study)
PubMed 24702712 · doi:10.1111/dom.12299
What was done
Skeletal muscle biopsy samples (~60 mg) from healthy female volunteers were incubated ex vivo for 30 minutes under four conditions: basal control, insulin (60 µU/ml), recombinant human IL-6 (rhIL-6, 4 ng/ml), or rhIL-6 (4 ng/ml) combined with recombinant human IL-6 receptor (rhIL-6R, 100 ng/ml). Glucose transport was measured across conditions, and Western blot analyses were performed to evaluate phosphorylation of key signaling proteins: PKB/Akt, AMPK, and mTOR.
What was found
Insulin increased glucose uptake 1.85-fold (p < 0.05) and stimulated phosphorylation of PKB/Akt (0.98 ± 0.23 phosphorylated:total, p < 0.05) and AMPK (1.49 ± 0.13, p < 0.05). IL-6 alone did not stimulate glucose uptake. The combination of rhIL-6 and rhIL-6R induced a 1.5-fold increase in glucose uptake (p < 0.05), increased AMPK phosphorylation (0.95 ± 0.19, p < 0.05), and increased mTOR phosphorylation 4-fold relative to control, insulin, and IL-6 alone (p < 0.05), without stimulating PKB/Akt phosphorylation.
Why it matters
It demonstrates that IL-6 combined with its soluble receptor stimulates skeletal muscle glucose uptake through an AMPK- and mTOR-associated pathway independently of classical insulin-activated PKB/Akt signaling.
Limits
The abstract does not state the number of human donors (sample size). The findings derive from a short 30-minute ex vivo incubation of isolated muscle tissue from female volunteers only, which may not capture in vivo physiology or chronic exposure effects.
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