“I think many people recognize that CRP is only a small marker and may not be that sensitive a marker,” says Dace L. Trence, MD, Director of the Diabetes Care Center at the University of Washington Medical Center in Seattle. “We know that CRP can go up with a cold and then come right back down again, so it isn’t as simple as taking one test to check whether or not inflammation was going on; you wouldn’t have any symptoms, and that’s the problem.”
The test may be useful for people at moderate risk for heart disease to determine if they are at more risk than they thought, but Dr. Fonseca does not recommend testing the average person with obesity and/or diabetes. “The American Heart Association and the Centers for Disease Control and Prevention suggest screening with CRP for people at moderate risk for heart disease, but we’re not making recommendations about people at moderate risk for diabetes because we don’t know that any intervention to suppress inflammation will do any good.”
Inflammation, heart disease, and diabetes
Scientists are just beginning to understand how widespread the effects of chronic inflammation may be throughout a person’s body and what kind of damage it might do. They have a tighter grasp on what it does to blood vessels, however, which is where most of the research has focused. In a nutshell, chronic inflammation stresses arterial walls and is associated with the development of atherosclerosis, the buildup of fatty deposits in arterial linings.
It’s also becoming clearer that inflammation may be behind insulin resistance, the reduced ability of the cells to respond to insulin, which is a cause of high blood glucose in Type 2 diabetes. Markers that indicate inflammation and are predictive of heart disease are higher in people with Type 2 diabetes than in those without, even when matched with other risk factors for inflammation such as body-mass index, smoking, and sex. “In fact,” says Dr. Fonseca, “in people with diabetes, almost every tissue has a little bit of inflammation.”
Lifestyle habits over time may play a role in chronic inflammation. “We think that while there are clearly genes involved in the development of diabetes, there are also environmental components,” says Allison B. Goldfine, MD, Section Head of Clinical Research at the Joslin Diabetes Center in Boston and the lead researcher investigating the impact of an anti-inflammatory medicine on diabetes (see “Salsalate Study”). “The sedentary lifestyle and excess caloric intake that lead to excess weight gain promote this chronic, sub-acute inflammation, which then participates in the development of Type 2 diabetes.”
It’s possible that simply being overweight triggers inflammation. “Maybe lack of exercise [is a cause],” says Dr. Trence. “This is an area where there are a lot more questions than answers, and I think people are beginning to recognize that there may be various factors that play a role.”
Whatever causes inflammation in the first place, its presence creates an unfortunate set of consequences in a few very concrete ways. “The immediate contributions of the inflammatory state are, first, atherosclerosis, heart attack, and stroke; and second, insulin resistance and Type 2 diabetes,” says Paresh Dandona, MD, Director of the Diabetes-Endocrinology Center of Western New York and Chief of the Division of Endocrinology at the Medical School of the State University of New York at Buffalo. “Of course, Type 2 diabetes feeds into heart attack and stroke as well. The rates of heart attack and stroke are two to four times greater in the diabetic population.”