Risk of diabetes increases after colectomy, study finds

Denmark: People who have undergone colectomy are at increased risk of developing type 2 diabetes (T2D), according to a new study published in the journal eLife. The study implies that the colon may play a role in regulating the body's blood sugar level. The researchers hope this new knowledge may pave the way for new ways of preventing and treating the disease.

Anders B. Jensen, Novo Nordisk Foundation Center for Protein Research, University of Copenhagen, Copenhagen, Denmark, and colleagues conducted the study to determine whether colectomy is associated with the development of T2D.

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In the large study, the researchers have shown what happens when patients have parts of or the entire colon removed. The researchers have seen an increased risk of developing type 2 diabetes following this type of surgery. This suggests that the colon plays a role in regulating the blood sugar level.

For the study, the authors studied data from Danish registers of just over 46,000 patients who have either had the entire colon or parts of it removed. This data was compared to data of just under 700,000 comparable patients who in the same period had undergone surgery for something else than the disease in the gastrointestinal tract. The study is an example of how researchers can use real human treatment in the health care system as a kind of 'model.' The data studied by the researchers span an 18-year period beginning at the time of the operation.

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Key Findings:

• Patients who had the entire or left side of the colon removed showed an increased risk of developing T2D in the 18 years following the operation compared to patients who had undergone surgery in different parts of the body.


• Patients who had had the right or middle horizontal part of the colon removed showed no increased risk of developing diabetes, though.

'We know that the colon houses large numbers of gut bacteria and hormone-producing cells, but we still do not know which role they play in regulating the blood sugar level. We hope our study will facilitate further research into the significance of the colon in blood sugar regulation and diabetes development', says co-author Kristine Allin, Head of Section and Staff Doctor at the Center for Clinical Research and Prevention at Bispebjerg and Frederiksberg Hospitals.

'The surgical procedures these patients have undergone represent the "trial", and the results are then determined from the many data held in the Danish registers. Researchers often use animal testing to identify a connection, before determining whether the results also apply to humans. Here we are looking directly at surgery on humans, and we do not have to worry about whether the findings also apply to humans. The human as a 'model organism' is a concept that is gaining ground, ensuring that new patients benefit from experience and data collected through 20 years of treatment of previous patients', says co-author and Professor Søren Brunak from the Novo Nordisk Foundation Center for Protein Research.

This suggests that the left side of the colon plays a role in regulating the body's blood sugar level. The colon is full of gut bacteria and microbes, and some other studies indicate that a changed composition of these microbes - like when part of the colon is removed in surgery - may play a role in the development of various diseases, aside from infections.

'The greater majority of the body's microbes are found in the colon, so it is relevant to look at what happens after the colon or part of it is removed. In a previous study, we saw no significant connection with the risk of developing cardiovascular diseases. We were therefore rather surprised to see so relatively massive an increase in the risk of developing type 2 diabetes. In fact, the increased risk corresponds to the effect of having three times as high a BMI', says co-author and Professor Thorkild I.A. Sørensen from the Department of Public Health and Novo Nordisk Foundation Center for Basic Metabolic Research.