Semaglutide Effects on Insulin Sensitivity and β-Cell Function in Patients With Schizophrenia, Prediabetes, and Obesity Treated With Second-Generation Antipsychotics: Findings From the HISTORI Trial, a 30-Week Randomized, Placebo-Controlled Trial With Semaglutide 1.0 mg Weekly.

OBJECTIVE: To examine the effects of semaglutide on insulin sensitivity, insulin resistance, and β-cell function and explore whether these changes were mediated by weight loss in overweight or obese individuals with schizophrenia and prediabetes receiving second-generation antipsychotics. RESEARCH DESIGN AND METHODS: In this 30-week, double-blind trial, 154 participants were randomized to semaglutide (n = 77) or placebo (n = 77); 141 (91.5%) completed the study. Baseline and end-of-study assessments included fasting glucose, insulin, C-peptide, HOMA2 of β-cell function, HOMA2 of insulin sensitivity, HOMA of insulin resistance, and body weight. RESULTS: Participants (56% women, mean age 38.3 years) provided complete insulin data in 131 cases. Compared with placebo, semaglutide significantly reduced fasting glucose (-0.87 mmol/L [95% CI -1.15, -0.59]; P < 0.001), improved insulin sensitivity (8.60 [5.82, 13.65]; P = 0.001), and lowered insulin resistance (-0.69 [-1.00, -0.20]; P = 0.006). Mean weight loss was 9.2 kg and mediated improvements in insulin sensitivity (estimate 7.82; P = 0.01) and insulin resistance (estimate -0.75; P = 0.01). Nonsignificant trends were observed toward reduced fasting insulin (-52.3 pmol/L; P = 0.11) and C-peptide (-182.9 pmol/L; P = 0.096), with a modest, nonsignificant increase in β-cell function (8.10; P = 0.19). CONCLUSIONS: Semaglutide significantly improved insulin sensitivity, reduced insulin resistance, lowered fasting glucose, and promoted substantial weight loss in patients with antipsychotic-induced metabolic disturbances. Weight loss partly mediated the metabolic improvements, while β-cell function remained largely unchanged. These findings support semaglutide as a potential strategy for mitigating metabolic dysfunction in this high-risk population.