In my last post, I explained the importance of normal glucose metabolism.  In this post, I’ll talk about a condition of impaired (faulty) glucose metabolism called prediabetes.  Many people think that the only danger of prediabetes is that a person may go on to develop diabetes.  Unfortunately, research indicates that prediabetes poses grave dangers to people’s health in other ways as well.

The American Diabetes Association developed guidelines for the diagnosis of glucose impairment during a conference in 2006 (Nathan, 2007).  Here is a table that summarizes these guidelines.  You need to know that OGTT stands for “oral glucose tolerance testing.”  This typically involves drinking a liquid mixture containing 75 grams of glucose and water.

Most people are screened for diabetes with a blood test that measures their blood glucose levels after fasting.  Usually, an OGTT test is not given unless fasting glucose measurements are abnormal.  Unfortunately, research suggests that not all people with prediabetes have impairments in both fasting glucose and responses to OGTT (Cubeddu and Hoffman, 2010).  According to this research, only about 20 to 30% of people who have impaired glucose tolerance, based on an OGTT, also have impaired fasting glucose.  This means, that many, many cases of prediabetes may be missed. 

This is significant, because a number of studies link impaired glucose metabolism to other disorders, even in those people without diabetes.  Hu et al. (2002) followed almost 120,000 female nurses for 20 years.  These women were 30 to 55 years old when he started his research and apparently free of cardiovascular disease.  Women who developed prediabetes had a significantly higher incidence of heart attack, stroke, and coronary artery disease than those who did not develop this disorder.  Haffner et al. (1990) found that subjects who developed prediabetes had significantly higher rates of elevated LDL (the bad guy) cholesterol, elevated triglycerides, lower levels of HDL (the good guy) cholesterol, and higher blood pressure than those with normal glucose metabolism.

Elevated glucose levels damage the cardiovascular system by promoting atherosclerosis in large blood vessels.  When this happens, plaques of fat infiltrate the walls of blood vessels and eventually reduce blood flow in those vessels.  In addition, pieces of these plaques can break off, traveling to smaller blood vessels in the brain, causing a stroke, or the heart, causing a heart attack.  A study by Kurihara et al (2013) found that prediabetic patients had significantly higher levels of atherosclerosis than patients with normal glucose metabolism.  In fact, those with prediabetes had similar amounts of atherosclerotic plaques as those patients with full blown diabetes. 

Elevated glucose levels also damage smaller blood vessels called capillaries.  This is especially true of the capillaries in the kidneys and eyes.  It’s important to know that high levels of blood glucose can damage the kidneys and eyes by directly harming their capillaries and by the effects of high blood pressure, which tends to be higher in those with prediabetes. Here’s a link to a Web site that has more information about prediabetes and the blood vessels in the kidneys:    http://www.kidney.org/news/KidneyCare/summer10/PreDiabetes.cfm.   And here is a link to a Web site that has more information about prediabetes and capillaries of the eyes.  http://prediabetescenters.com/prediabetes-101/symptoms-of-prediabetes/vision-change/

Several studies also suggested a link between disorders of glucose metabolism and cancer (Sayda et al., 2002; Ehrmann-Josko et al., 2006; Stattin et al., 2007; Danker, et al., 2007).  In these studies, subjects who eventually developed prediabetes had a significantly higher risk of also developing cancer than normal subjects.  It is possible that both higher levels of blood glucose and higher levels of insulin production may promote the growth of cancerous cells.

The connection between prediabetes and the eventual development of diabetes is well established.  In a study by Abdul-Ghani et al. (2008), for example, about half of subjects with prediabetes went on to develop diabetes within eight years.  Diabetes is a huge risk factor for the development of cardiovascular disease, kidney disease, nerve damage, and blindness, so this research points out the seriousness of prediabetes.  Since the American Diabetes Association (2013) estimates that 79 million Americans currently have prediabetes, and that over 90% of Americans with prediabetes are unaware of their condition, the implications are staggering.

 In my next post, I’ll discuss ways to lower the risk of developing prediabetes.

References:  Please email me if you would like the complete references for the works cited above.