Scientists have explored how bacteria within the bellies of babies and toddlers might contribute to the development of type 1 diabetes.
In a new study, researchers charted developing gut bug populations of young children who were later diagnosed with the condition, which affects an estimated 10,000-20,000 New Zealanders.
Children who get type 1 diabetes have certain kinds of genes, but not everyone with the genes develops the condition.
Scientists are looking at whether the development of the gut microbiome from birth to childhood may play a protective, predisposing or even triggering role – potentially offering a kind of microbial "security blanket".
The latest results come from an umbrella study called Teddy (The Environmental Determinants of Diabetes in the Young), in which researchers collected monthly stool samples, as well as blood samples and diet, health and lifestyle records to generate the richest data set of its kind to date.
The children were far-flung, living in Finland, Sweden, Germany, and three US states - Washington, Colorado and Georgia - where the Teddy's six collaborating research centres are based.
The new study, one of two analyses from Teddy just published in the scientific journal Nature, used bacterial gene sequencing to track the gut microbiome of mostly Caucasian children with type 1 diabetes from three months of age until they were diagnosed – usually at 2 to 5 years old – and compared it to that of healthy children without diabetes.
A third group of children had a pre-diagnostic stage called islet autoimmunity, or IA.
Analysis of nearly 11,000 stool samples from the 783 children revealed how much the variety and mix of gut bugs change and develop in early childhood.
Researchers found pronounced individual differences – suggesting unique gut bug populations evolve from a very young age – but also subtle group differences.
Compared to the IA children, the healthy cohort had more Lactobacillus rhamnosus, common in fermented milk products such as yoghurt, and linked to better gut digestion.
They also harboured more bacterial genes that fuel short-chain fatty-acid production, compared to both the IA and type 1 diabetes children.
Short-chain fatty-acids are beneficial to gut health and immune function and are produced only by gut microbes.
"Past, smaller studies have identified shifts in the gut microbiome before the onset of type 1 diabetes, suggesting that the gut microbiome might be a predisposing or even a triggering factor," study lead author Dr Tommi Vatanen said.
Vatanen conducted the study while based at the Broad Institute of MIT and Harvard, and has since joined the Liggins Institute at the University of Auckland as a Research Fellow.
Previous investigations in Teddy have also raised the idea that probiotics may be protective against type 1 diabetes in children with the highest genetic risk.
In Nordic countries, probiotics are sometimes recommended for babies and young children, and many parents give their babies Vitamin D and probiotics drops with breastmilk.
"We cannot say with certainty that probiotics are protective yet, though," Vatanen said.
"First, we need to run controlled clinical trials of, for example, carefully selected pro- and/or pre-biotic supplements.
"It also may be possible to protect children from type 1 diabetes by radically changing their gut microbiome by way of a gut bugs transfer – another exciting research direction."
The researchers also found geographical differences in children's gut bugs.
For example, Finnish children had, on average, more Bifidobacterium breve, which is sometimes used as a probiotic and belongs to a group of bacteria known to be beneficial to gut health.
"This could be due to differences in the mother's gut microbiome, which she transfers to the baby, or to differences in breast milk and early feeding in general."
Vatanen was also one of the authors of a second Teddy study published in the same issue of Nature, which analysed 12,500 stool samples from 903 children and identified three distinct phases of gut microbiome development, influenced by breastfeeding and other environmental factors.