Anti-TNF treatment decreases insulin receptor substrate (IRS)-1 Ser312 phosphorylation and increases AKT phosphorylation in patients with active rheumatoid arthritis (RA) and high insulin resistance. (A) Seven patients with active RA received anti-TNF treatment for 12 weeks. Protein extracts from PBMCs were analyzed by western blotting for the Ser312-phosphorylated form of IRS-1 at weeks 0 and 12 of treatment. All but one patient demonstrated decrease in IRS-1 phosphorylation at Ser312. (B) Quantitative analysis (protein densitometry) showed that median phosphorylated IRS-1 normalized for β-actin levels were reduced from 0.96 to 0.57 (arbitrary units) (Wilcoxon signed ranks test, P = 0.043). (C) Decrease in disease activity following anti-TNF treatment (from median DAS28 7.4 to 6.3, P = 0.049). (D) Improvement in insulin resistance following anti-TNF treatment (from median HOMA-IR 7.6 to 3.6, P = 0.028). (E) Protein extracts from peripheral blood mononuclear cells (n = 7 RA patients) were analyzed by western blotting for Ser473- phosphorylated AKT at weeks 0 and 12 of anti-TNF therapy. (F) Phosphorylated AKT levels, normalized for β-actin, increased in all RA patients from a median 0.24 (arbitrary units) at week 0 to 0.94 at week 12 (P = 0.001).