Diet and Exercise Reduces CVD Risk in Pre-Diabetics
posted 06/18/03

Follow-up analysis of data from the Diabetes Prevention Program (DPP), showed that diet and exercise can be more effective than pharmacologic therapy at warding off cardiovascular disease in patients with impaired glucose tolerance.

The findings parallel those of the landmark DPP trial of 3,234 overweight people with pre-diabetes. Those results, reported last year, showed that at three years, participants who modified their lifestyles decreased their risk of developing type 2 diabetes by 58% compared with those receiving placebo. The use of metformin also reduced risk, although not as much: Participants taking the drug were 31% less likely to develop diabetes compared with those on placebo.

Now, the new analysis shows that diet and exercise also reduce indirect measures of heart disease — especially subclinical inflammation as indicated by a significant drop in C-reactive protein (CRP) levels — more than metformin (P < .05).

Steven M. Haffner, a professor of medicine at the University of Texas Health Science Center (UTHSC) in San Antonio, reported the findings at the American Diabetes Association 63rd Scientific Sessions. Michael Stern, MD, who moderated the session, said the new findings are an important step toward demonstrating that interventions can prevent not only diabetes, but also its complications.

"DPP showed that we can prevent diabetes, but we still didn't know if we can prevent the complications of diabetes, which are what causes morbidity and mortality," said Dr. Stern, who is also a professor of medicine at UTHSC-San Antonio but was not involved with the trial. "Now we see that interventions do reduce indicators of cardiovascular disease, though we still have long-term follow-up planned to confirm if this translates into actual reduced risk," he said.

DPP randomized participants to one of three arms. Participants in the lifestyle intervention group aimed to lose 7% of their body weight, in part by lowering their fat intake to less than 25% of their caloric intake and exercising moderately 30 minutes a day, five days a week. The second arm received 850 mg of metformin twice a day, while the third group received placebo. Both the metformin and placebo groups also received information on diet and exercise but no counseling efforts.

For the new analysis, the researchers looked at three markers of cardiovascular disease risk — CRP, tissue plasminogen activator (TPA), and fibrinogen — that also have been shown to affect the risk of developing diabetes, Dr. Haffner said.

Baseline CRP levels were "extraordinarily high," particularly in women, he said. Noting that American Heart Association guidelines consider levels of higher than 3.0 mg/dL to be elevated, he said that baseline levels in the entire cohort were 5.9 mg/dL. When broken down by sex, CRP levels in men and women were 3.2 mg/dL and 7.2 mg/dL, respectively. From baseline to one year, CRP levels in men decreased 28% in the lifestyle intervention group compared with 5% in the metformin group and 3% in the placebo group, the study showed. In women, CRP levels decreased 23% in the lifestyle group, 12% in the metformin group, and 1% in the placebo group.
TPA levels, which averaged around 11 mg/dL in both sexes in all three arms at baseline, dropped 18.9%, 15.5%, and 3.0% in the lifestyle, metformin, and placebo groups, respectively.

And fibrinogen levels, which averaged 380 ng/dL to 386 ng/dL in the three arms at baseline, decreased by 1.9% and 1.0% in the lifestyle and metformin groups, respectively, while increasing by 2.4% in the placebo group. For all three measures, lifestyle intervention was associated with a more significant decrease in values than metformin (P < .05), Dr. Haffner said.

Seeking to find out why CRP levels dropped so dramatically among participants on a diet and exercise program, the researchers used a multiple linear regression model to look at fasting glucose, two-hour glucose during an oral glucose tolerance test, insulin resistance, body mass index (BMI), waist circumference, and physical activity. The researchers found that weight loss, as indicated by a decrease in BMI, was the strongest predictor of CRP change in both men and women (P,/i> < .001), Dr. Haffner said. Interestingly, although maximal weight loss was reached at six months, CRP continued to decline throughout the one-year study, he added, suggesting that some other factor may also be at play.

The next step, he said, is to determine whether the larger drops in inflammation, fibrinolysis, and coagulation associated with lifestyle modification translate into slower progression of atherosclerosis. A 10-year follow-up study to answer that question and look at the incidence of other CVD events in all three groups is now underway.

Source: Diabetes In Control Dot Com: ADA 63rd Scientific Sessions: Abstract 79-OR. Presented June 14, 2003.

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