05. Administration of a 2.5 mg/kg intravenous bolus of hCRP maintained serum hCRP Selleckchem PD332991 concentration at a stable level throughout the 3-hour time course

of the clamp procedure (Supporting Information Fig. S1). In contrast to vehicle-treated rats in which hCRP was undetectable, hCRP-treated rats had a mean hCRP serum level of 40.2 mg/L at 5 minutes and the level declined slightly to a mean of 33.7 mg/L at 3 hours postadministration. By design, blood glucose levels were maintained at basal levels during clamps and there was no difference in glucose concentration between hCRP- and vehicle-treated rats (Fig. 1A). The glucose infusion rate (GIR) required to maintain euglycemia was significantly lower during the last 30 minutes of clamps in hCRP-treated rats compared with vehicle (P < 0.01, Fig. 1B), demonstrating hCRP-induced insulin resistance. During the last 30 minutes of clamps, EGP was suppressed by insulin to a much lesser extent in hCRP-treated rats than in vehicle-treated rats (suppression of EGP as a percentage of basal: 45.6 ± 6.6% versus 88.4 ± 7.6%, respectively, P < 0.01, Fig. 1C), whereas Rd, which reflects whole-body glucose uptake, was similar between groups (Fig. 1D). Therefore, hCRP-induced insulin resistance was accounted for entirely by hepatic insulin resistance. Such effects were not due to the presence of other components in the hCRP preparations because human

serum albumin, administered exactly the same way as hCRP, did not affect these measurements during clamps (Supporting Information Fig. S2). Plasma insulin increased, whereas free fatty acid (FFA) and glucagon decreased to a similar extent during clamps in hCRP- and vehicle-treated rats (Supporting Information Table S1), indicating that the effect of

hCRP on insulin sensitivity was not mediated indirectly by any of these factors. Total protein levels of IRS-1 were similar between groups. However, hCRP markedly reduced insulin-stimulated IRS-1 pY (P < 0.05) and IRS-1/PI3K association (P < 0.05) (Fig. 2A). hCRP exerted similar effect on IRS-2 pY (P < 0.01) and IRS-2/PI3K association (P < 0.01) (Fig. 2B). Total Akt did not differ between Protirelin groups but basal Ser473 phosphorylation was elevated (P < 0.01) and insulin-stimulated Ser473 phosphorylation was decreased (P < 0.05) in hCRP-treated rats. hCRP did not affect either basal or insulin-stimulated Akt Thr308 phosphorylation (Fig. 2C). Compared with vehicle, hCRP-treated rats displayed a significant increase in IRS-1 Ser612 phosphorylation (P < 0.05) and a nonsignificant increase trend in Ser307 phosphorylation (Fig. 3A). hCRP stimulated phosphorylation of ERK1/2 (P < 0.05) and p38 MAPK (P < 0.01) (Fig. 3B,C) but not JNK (Supporting Information Fig. S3) in the liver. We quantified plasma levels of TNF-α, IL-6, leptin, and adiponectin before and after hCRP treatment. None of these cytokines were affected by hCRP (Supporting Information Table S2).