FIG. 4.

Acute physiological elevation of IL-6 reduces myocardial glucose metabolism by suppressing AMPK and IRS-1. Mouse recombinant IL-6 or saline (control) was intravenously infused into C57BL/6 mice for 4 h, and heart samples were taken for analysis. A: Tyr⁷⁰⁵-phosphorylation of STAT3 normalized to total STAT3 protein level was increased in heart following IL-6 infusion. B: Basal myocardial glucose uptake was reduced following IL-6 infusion. C: A 2-h hyperinsulinemic-euglycemic clamp was performed during the final 2 h of IL-6 or saline infusion in C57BL/6 mice. Acute IL-6 infusion reduced insulin-stimulated glucose uptake in heart. D: Total AMPK protein levels normalized to β-actin were reduced in the heart of IL-6 infused mice. E: IL-6 infusion reduced Thr¹⁷²-phosphorylation of AMPK normalized to β-actin in heart. F: Insulin-stimulated tyrosine phosphorylation of IRS-1 normalized to IRS-1 protein levels in heart was reduced following IL-6 infusion. Values are means ± SE for six to eight mice in each experiment. *P < 0.05 vs. control.