Influencing the Insulin System by Placebo Effects in Patients with Diabetes Type 2 and Healthy Controls: A Randomized Controlled Trial

Abstract

Objective The objective of this study was to investigate whether placebo effect induced by pharmacological conditioning with intranasal insulin can affect glucose, insulin, C-peptide, hunger, and memory in patients with diabetes type 2 and healthy controls. Methods Placebo effect was induced by pharmacological conditioning. Thirty-two older patients (mean age = 68.3 years) with diabetes type 2 and age-and sex-matched thirty-two healthy older adults (mean age = 67.8 years) were randomly assigned to a conditioned or a control group. On day 1, conditioned group received six administrations of intranasal insulin with a conditioned stimulus (CS; smell of rosewood oil), whereas the control group received a placebo with the CS. On day 2, both groups received a placebo spray with the CS. Glucose, insulin, and C-peptide were repeatedly measured in blood. Hunger and memory were assessed with validated measures. Results Intranasal insulin stabilized dropping glucose levels in patients (B = 0.03, SE = 0.02, p =.027) and healthy men (B = 0.046, SE = 0.02, p =.021), and decreased C-peptide levels in healthy controls (B = 0.01, SE = 0.001, p =.008). Conditioning also prevented the drop of glucose levels but only in men (both healthy and patients; B = 0.001, SE = 0.0003, p =.024). Conditioning significantly decreased hunger in healthy participants (B = 0.31, SE = 0.09, p