IRS1 and morbid obesity: Analysis of the gene expression of key players of the IRS1/PI3K signaling cascade (Figure 1) showed a reduced expression of IRS1 in all three groups of patients with morbid obesity compared to non-obese patients, with only the MO-low-IR and MO-high-IR groups showing significant differences (p = 0.017 and p = 0.02, respectively).