INS and type 2 diabetes mellitus: Also, the insulin-stimulated serotonin response was significantly lower in patients with type 2 diabetes (Fig. 2): The percentage increase in blood-flow after co-infusion of insulin compared to serotonin alone was 45.96 ± 11.56%; 67.40 ± 18.11% and 84.57 ± 25.73% in the healthy control group and 26.48 ± 7.74%; 26.40 ± 11.52% and 19.75 ± 13.87% (p = 0.02) in the group of patients with type 2 diabetes.