Early-Life Gut Microbiome Changes May Help Assess Type 1 Diabetes Risk

Type 1 diabetes (T1D) affects more than 9 million people worldwide, including 1.8 million children and adolescents, and often begins years before symptoms appear. Early identification of children who are progressing toward disease remains difficult even when genetic risk is known. The gut microbiome is increasingly studied as a window into early-life immune dysregulation. A new longitudinal study now shows that distinct patterns of gut microbiome maturation in infancy and early childhood are associated with markedly different T1D risks.

Researchers at Mass General Brigham, the Broad Institute of MIT and Harvard, and the Harvard T.H. Chan School of Public Health analyzed gut microbiome development in children at elevated genetic risk for T1D. By examining serial stool samples collected from infancy through early childhood, the team identified distinct patterns of microbiome maturation and explored their relationship to disease development. The findings were published in Nature Metabolism on September 21, 2026.

Image: Type 1 diabetes affects more than 9 million people worldwide and can begin years before symptoms appear, making early identification of at-risk children difficult (Image Credit: iStock)

The longitudinal observational TEDDY Study followed 887 high‑risk children and generated more than 12,000 stool samples across the first six years of life in Finland, Germany, Sweden, and the United States. Disease progression was counted when islet autoimmunity was first detected or when T1D was diagnosed. Repeated sampling was required to uncover the associations.

Three trajectories emerged: early‑matured, late‑matured, and early‑plateaued. Early‑matured profiles showed richer diversity and a faster shift from milk‑adapted taxa such as Bifidobacterium toward fiber‑degrading species. Children whose microbiomes plateaued early had about triple the risk of T1D or its preclinical autoimmunity versus peers with standard maturation; results were similar for the presymptomatic and clinical endpoints.

Host genetics altered how strongly the late‑matured pattern related to risk, while the early‑plateaued pattern conferred higher risk regardless of genetic background. The authors emphasize that the work provides strong prospective evidence but cannot establish causality and warrants evaluation in the general population. They also note that clinical trials are needed before any microbiome‑directed prevention strategies could be integrated into pediatric care.

“By analyzing interactions between the microbiome and host genetics, we found genetic variants, particularly those involved in antimicrobial and antiviral immune responses, that shaped how strongly the late-matured pattern was related to disease risk. The early-plateaued pattern, by contrast, carried higher risk regardless of genetic background,” said Danyue Dong, Ph.D., a postdoctoral research fellow in the Channing Division of Network Medicine at Mass General Brigham.

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