MARVEL study
Microbiome, Residual β-cell Function and Long-term Complications in Type 1 Diabeter
Background and Rationale
Despite major advances in glucose monitoring and insulin therapy, people with type 1 diabetes (T1D) remain at risk for long-term microvascular and macrovascular complications. Interindividual differences in complication burden are only partly explained by glycaemic control, suggesting that additional biological factors play a role. Increasing evidence points toward the gut microbiome as a key modulator of metabolic and inflammatory pathways that may influence cardiovascular disease and diabetes-related organ damage. In parallel, residual endogenous insulin production, even at low levels, has been associated with improved metabolic stability and reduced complication risk. How these factors interact over long-term follow-up in people with established T1D is currently insufficiently understood.
To address this knowledge gap, we have set up the MARVEL study. By combining long-term follow-up with detailed biological and phenotypic data, MARVEL aims to improve understanding of non-glycaemic determinants of diabetes complications and to identify potential microbiome-related pathways involved in cardiovascular and microvascular disease in T1D. These insights may support the future development of personalized risk stratification, targeted preventive strategies, and more individualized approaches to complication prevention and management in type 1 diabetes.
Study Objectives
The MARVEL study aims to investigate whether:
- The composition and characteristics of the gut microbiome are associated with the presence and development of chronic complications in adults with type 1 diabetes, including cardiovascular disease and damage to the nerves, kidneys, eyes, and feet.
- Residual endogenous insulin production is associated with a lower risk of long-term complications.
- Interactions between gut microbiota, metabolic control, and residual β-cell function may help explain interindividual differences in complication trajectories.
Study Design & Study Population
MARVEL is a longitudinal observational cohort study in approximately 5,000 adults with type 1 diabetes. Participants will undergo one baseline study visit and follow-up assessments after 3, 6, and 10 years, which can largely be integrated into routine diabetes care to minimize participant burden.
The study includes adults aged 18 years or older with type 1 diabetes, recruited through Diabeter NL (~2,500 participants) and the Amsterdam Diabeter Center (~2,500 participants). The study relies on long-term participant engagement and aims to generate clinically meaningful insights for the broader T1D community.
Study Procedures and Data Collection
At baseline and follow-up visits, the following data are collected:
- Blood samples (can coincide with routine laboratory assessments)
- Urine samples
- Stool samples for gut microbiome analysis
- Continuous glucose monitoring (CGM) data extraction
- Dietary assessment using a food diary
- Standardized questionnaires on health status and lifestyle
This multimodal dataset enables integrated analyses of metabolic control, microbiome composition, residual insulin secretion, and long-term clinical outcomes.
Inquiries about this study can be sent to research@diabetercentrumamsterdam.nl or research@diabeter.nl