A study published in the open-access journal PLoS Medicine finds that levels of C-reactive protein (CRP) in the blood are not likely to cause diabetes. Previous research has suggested that raised levels of the protein are linked to an increase in diabetes risk, but this latest research conducted by Eric Brunner (Royal Free and University College London Medical School, London) and colleagues suggests that the association is not causal.

Affecting about 200 million people in the world, diabetes is a condition characterized by high blood sugar (glucose) levels in the blood that often leads to problems with several organs and a shorter lifespan. In type 2 diabetes (also called adult-onset), the body becomes resistant to insulin, blood sugar levels increase, and the pancreas responds by producing more insulin. Diabetes is fully developed when the pancreas malfunctions and insulin secretion decreases. Being overweight is a major risk factor for diabetes, and increased body fat causes mild, chronic tissue inflammation – leading to further insulin resistance. It is also known that people with high levels of the inflammatory protein CRP are at an increased risk of developing diabetes. It has been proposed that inflammation causes diabetes, and a drug that reduces the level of CRP in the blood could also decrease the risk of developing diabetes.

Brunner and colleagues used a method called Mendelian Randomization to test if inflammation is a cause of diabetes. From a sample of 50,000 people from the Whitehall II study, the researchers were able to measure blood CRP levels. They also used the ”homeostasis model assessment-insulin resistance” (HOMA-IR) method to measure long-term blood sugar control as well as insulin sensitivity from blood glucose and insulin measurements. Thirdly, the investigators analyzed three “single polynucleotide polymorphisms” in CRP to track inherited genetic blocks. To control for the effects of other variables, the researchers included several potential confounding factors in their model such as obesity, blood pressure, and socio-economic position – all play a role in the development of diabetes.

Results from the study indicate that blood CRP levels are not responsible for the development of insulin resistance or diabetes (in European populations). Further, drugs that target against CRP are unlikely to prevent or delay the onset of diabetes.

Inflammation, insulin resistance and diabetes – Mendelian randomization using CRP haplotypes points upstream
Brunner EJ, Kivimäki M, Witte DR, Lawlor DA, Davey Smith G, et al.
PLoS Medicine (2008). 5(7): e155.
doi:10.1371/journal.pmed.0050155
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About PLoS Medicine

PLoS Medicine is an open access, freely available international medical journal. It publishes original research that enhances our understanding of human health and disease, together with commentary and analysis of important global health issues. For more information, visit http://www.plosmedicine.org

About the Public Library of Science

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Written by: Peter M Crosta