August 27, 2015

expert reaction to study on antibiotics and type 2 diabetes

A study published in the Journal of Clinical Endocrinology & Metabolism is reporting an association between antibiotic use and the risk of diagnosis of type 2 diabetes. Although the link can’t be shown to be causal, the study suggests that a possible mechanism behind the association could be the impact of antibiotics on the microbiome of the gut.

Prof Kate Gould, General Secretary of the British Society for Antimicrobial Chemotherapy, said:

“The data presented here is very interesting, but at present this research doesn’t show a definite causal association between antibiotics use and type 2 diabetes. I think before we draw any firm conclusions, there are further research questions that need to be answered.

“The authors’ conclusion that it was narrow spectrum antibiotics that had a greater risk of type 2 diabetes is slightly counterintuitive for a Microbiologist, I would expect that the broader spectrum antibiotics would disrupt gut flora more. Some antibiotics have a greater effect on gut flora because of the way they are metabolised and excreted by the body. It would be interesting to look at the effects of antibiotics according to their metabolism, effects on gut flora, and their spectrum of activity, as they may have different impacts on the microbiome.”

Prof Mark Wilcox, Professor in Medical Microbiology, Leeds General Infirmary, said:

“The study data are interesting and are certainly provocative. It is plausible that the detrimental effects of antibiotics on the bacteria present in our gut, which actually outnumber our human cells, can lead to diseases that are due to malfunctioning of body control mechanisms. For example, this is known to explain why antibiotics are associated with C. difficile infection. Also, experiments in animals have shown that antibiotics can affect body weight and blood pressure.

“Whether antibiotic exposure can truly affect the risk of diabetes remains unknown. This latest study only shows a possible link between the two, rather that proving that antibiotics could cause diabetes. Importantly, the authors did not control for body weight when comparing people who received antibiotics with those who developed (type 2) diabetes. So, it is possible that the greater exposure of antibiotics found in people who went on to develop diabetes is actually a marker for people who were overweight and had more infections; obesity is known to increase the risk of a range of infections and, crucially, to increase the risk of diabetes. We therefore need more studies that can examine all of the possible reasons that could explain a link between antibiotics and subsequent development of diabetes. Lastly, patients who are in the early stages of diabetes, but in whom the diagnosis has not yet been made, are likely to be at increased risk of infection; this could also part-explain the association found in the latest study.”

Prof Jodi Lindsay, Professor of Microbial Pathogenesis, St George’s, University of London (SGUL), said:

“This paper adds to the growing evidence that antibiotic usage is linked to type 2 diabetes. A large study of UK patients earlier this year showed a link, and this new paper from Denmark reports a large case control study that provides even stronger evidence. We already know that patients with diabetes have an increased risk of developing infections and therefore they are more likely to be prescribed antibiotics to treat those infections. However, patients may have the early signs of diabetes, or it may be undiagnosed, and this might account for more antibiotic use. In this study, records for the previous 15 years prior to diabetes diagnosis indicated there was still a link. Such a long length of time makes us wonder if antibiotics are causing diabetes. However, this is not a study designed to identify the cause of diabetes, and at this point we do not know which is the chicken and which is the egg. There is some evidence from animal model studies that antibiotics could play a role in diabetes, and it is well known that antibiotics make livestock gain weight. Considering the enormous burden that diabetes has on our healthcare systems, it is important that further research is funded to investigate the role of antibiotics on the risk of developing diabetes.”

Prof Naveed Sattar, Professor of Metabolic Medicine, University of Glasgow, said:

“The study is interesting but findings are not unexpected since diabetes and those with higher sugar levels in advance of diagnosis are known to have more infections due to hyperglycaemia and potentially other risk factors for diabetes also increasing infection risk. The results cannot be taken to infer that antibiotics cause diabetes and any such speculation would be particularly weak in this case. Similarly, any mechanistic link to gut flora is also very weak. Careful reporting of this paper is therefore needed. The bottom line is that this paper confirms what we already know – multiple infections signal risk for diabetes. Nothing more, nothing less. If somebody is having multiple infections, then doctors should do a quick check for diabetes as part of the work up, especially if other obvious risk factors or other suggestive symptoms are also present. ”

* ‘Use of Antibiotics and Risk of Type 2 Diabetes: A Population-Based Case-Control Study’ Mikkelsen et al., published in Journal of Clinical Endocrinology & Metabolism on Thursday 27th August.

Declared interests

Prof Kate Gould: No conflicts of interest to declare.

Prof Mark Wilcox: I have no specific conflicts here.

Prof Jodi Lindsay: Advisory board for Pfizer on staphylococcal vaccines.

Prof Naveed Sattar: No conflicts of interest.