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NCT Number: NCT07252752

Dopamine and Insulin in Psychosis

Patients with schizophrenia have a high risk of developing metabolic disorders and current evidence points to an overlap in mechanisms underlying psychiatric symptoms and metabolic disturbances. The main goal of this study is to investigate effects of brain insulin on dopamine signaling and energy metabolism in patients with schizophrenia experiencing their first psychotic episode (FEP). To this end, patients with schizophrenia and healthy volunteers will undergo two [11C]-(+)-PHNO positron emission (PET) scans to measure the changes in dopamine receptor availability after nasally applied insulin, as well as single proton magnetic resonance spectroscopy (1H-MRS) to assess the impact of intranasal insulin on levels of glucose and glutamate in the hippocampus.

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Key information

Conditions

First Episode Psychosis (FEP) Mental Disorders Schizophrenia Schizophrenia Spectrum and Other Psychotic Disorders

Age range

18 year–40 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

All participants

  • age 18-40
  • Body mass index (BMI) range 18-25
  • good general health according to physical examination and medical history
  • absence of relevant abnormalities in laboratory screening, electrocardiogram (ECG) or vital signs
  • no regular use of drugs of abuse or alcohol based on history and urine drug screen

Patients only

  • diagnosis of schizophrenia or schizophreniform disorder according to DSM-5
  • ability to give informed consent
  • minimum Positive and Negative Syndrome Scale (PANSS) score of 55 with >3 on at least two or >4 on one PANSS psychosis item

Exclusion criteria

All participants

  • severe or unstable medical or neurological illness or clinically significant abnormality on screening laboratory studies or ECG
  • established diagnosis of type 1 or type 2 diabetes
  • current substance use disorder or regular recreational drug abuse (except nicotine and caffeine)
  • pregnancy or breastfeeding
  • history of head trauma resulting in loss of consciousness of >1min or requiring medical attention
  • presence of MRI exclusion criteria
  • if participation in this study would exceed annual radiation dose limits (30mSv)
  • clinically established diagnosis of intellectual disability

Healthy volunteers only

  • Psychiatric disorder according to Mini-International Neuropsychiatric Interview (M.I.N.I.)
  • Schizophrenia or bipolar disorder in first degree family members

Patients only

● Previous oral antipsychotic treatment for more than 2 weeks or previous treatment with antipsychotic depot preparation

Treatment and study plan

Intranasal insulin

Drug

160 IU intranasal insulin is administered using precision air pumps twice: 15 min prior to the PET scan and 35 min prior to the 1H-MRS scan

Placebo

Drug

Insulin-free dilution buffer is administered using precision air pumps 15 min prior to the PET scan

Low dose insulin infusion

Drug

2.5 mU/kg insulin in 100 ml isotonic saline is infused intravenously over 15min prior to PET scan when placebo is administered intranasally

placebo infusion

Drug

100 ml saline is infused intravenously over 15min prior to PET scan when insulin is administered intranasally

[11C] (+)-4-propyl-(+)-4-propyl-9-hydroxynaphthoxazine (PHNO)

Radiation

Each participant undergoes a 90-min [11C]-(+)-PHNO scan twice

Primary outcomes

  1. [11C]-(+)-PHNO BPND values

    Time frame: Assessed on two separate study visits within 5-12 days (scan duration: 90 min)

    Dopamine D2/3 receptor availability after intranasal insulin or placebo administration

  2. Hippocampal glucose and glutamate concentrations

    Time frame: Assessed during a single study visit (scan duration: 40 min in total)

    Hippocampal glucose and glutamate concentrations before and after intranasal insulin administration

Secondary outcomes

  1. Changes in blood-based parameters of energy metabolism

    Time frame: Assessed at baseline and at 15min intervals after instranasal insulin/placebo administration over a period of up to 90min

    Changes in concentrations of selected metabolic parameters (blood glucose, insulin, c-peptide, total cholesterol, HDL, LDL, trigycerides, ketone bodies) following intranasal insulin/placebo administration, assessed by venous blood sampling

  2. Hippocampal volumetric parameters

    Time frame: Assessed during a single study visit, at baseline (scan duration: 10min)

    Whole hippocampus and hippocampal subfield volumes assessed with structural MRI

Study contacts

Contact information is provided by the study sponsor or research team.

Irena Dajic

CONTACT

[email protected]

+43 1 40400 ext. 35470

Matthaeus Willeit

CONTACT

[email protected]

+43 1 40400 ext. 35470

Sponsors and collaborators

Lead sponsor

Medical University of Vienna

Other

Registry information

Official study title

Dopamine and Insulin in Psychosis: Imaging the Effects of Intranasal Insulin on Dopamine Transmission

Acronym: DIPS

Important dates

Study start
2026
Primary completion
2029
Study completion
2029
First posted
Nov 28, 2025
Registry last updated
Nov 28, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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