Similarly, muscle-specific ablation of signal transducer and activator of transcription 3 (STAT3), another transcription factor activated by proinflammatory cytokines, showed no effect on obesity-induced insulin resistance, as assessed by glucose tolerance test, clamp studies and measurement of 2-deoxyglucose uptake [30]. Here, STAT3 is linked to obesity due to melanocortin 4 receptor deficiency.