JDRF researchers at the University of Cambridge have found evidence that our immune systems change with the seasons – a finding that suggests a seasonal link to type 1 diabetes.
Scientists have known for some time that diagnosis rates of various conditions, including cardiovascular disease and type 1 diabetes, vary with the seasons. However, this is the first time that researchers have shown that this may be down to seasonal changes in how our immune systems function.
The study, published today in the journal Nature Communications, shows that the activity of almost a quarter of our genes differs according to the time of year, with some more active in winter and others more active in summer. This seasonality affects our immune cells and the composition of our blood and fat tissue.
‘This is a really surprising – and serendipitous – discovery as it could change how we identify the effects of the genes behind type 1 diabetes,’ said Professor John Todd, Director of the JDRF/Wellcome Trust Diabetes and Inflammation Laboratory at the Cambridge Institute for Medical Research.
‘In some ways, it’s obvious – it helps explain why so many diseases, from heart disease to mental illness, are much worse in the winter months – but no one had appreciated the extent to which this actually occurred. The implications for how we treat conditions like type 1 diabetes, and even how we plan our research studies, could be profound.’
An international team, led by researchers from the JDRF/Wellcome Trust Diabetes and Inflammation Laboratory, examined blood samples from over 16,000 people living in both the northern and southern hemispheres, in countries including the UK, USA, Iceland, Australia and The Gambia.
They found that thousands of genes were either more or less active depending on what time of year the samples were taken. One gene known as ARNTL was particularly interesting as previous studies have found that this gene suppresses inflammation, the body’s response to infection. The gene was found to be less active in winter, suggesting levels of inflammation should be higher during those months. Inflammation is a risk factor for a range of diseases – including autoimmune conditions such as type 1 – so it may be that in winter, the ‘threshold’ at which these conditions could be triggered could be more easily reached in those at greatest risk.
Karen Addington, Chief Executive of JDRF in the UK, said: ‘We have long known there are more diagnoses of type 1 diabetes in winter. This study begins to reveal why. It identifies a biological mechanism we didn’t previously know of, which leaves the body seasonally more prone to the autoimmune attack seen in type 1 diabetes.’
‘While we all love winter sun, flying south for the whole of each winter isn’t something anyone can practically recommend as a way of preventing type 1 diabetes. But this new insight does open new avenues of research that could help untangle the complex web of genetic and environmental factors behind a diagnosis.’