Components of Metabolic Syndrome Linked to Plaque Progression

Senior author Dr. Stephen J. Nicholls (Cleveland Clinic) states that, "Simply put, if you had the metabolic syndrome, you had twice as much [atheroma] progression as patients who didn't have the syndrome.... But if you then started to control for the individual risk factors, you no longer saw greater progression. In a nutshell, what this tells us is that the metabolic syndrome reflects the patient at high risk, but it doesn't suggest a direct effect of the syndrome itself on the vessel wall."

In this respect, the findings are consistent with previous population studies indicating that the syndrome probably doesn't represent a distinct disease entity, says Nicholls. It shows that "the metabolic syndrome continues to be important, but it's important in pointing to those with coronary disease who really need to have their major risk factors aggressively modified," he says.

In their systematic review of 3,459 patients participating in seven clinical trials that monitored coronary atheroma progression with IVUS, Bayturan et al compared patients with or without metabolic syndrome for clinical characteristics, coronary atheroma burden at baseline, and change on serial evaluation. A person with three of the following five components is described as having metabolic syndrome -- hyperglycemia, hypertriglyceridemia, hypertension, low HDL-C level, and central adiposity.

Relationships between plaque progression (>5% increase in percent atheroma volume [PAV]), metabolic syndrome, and its component risk factors were investigated.

More than half the patients had metabolic syndrome (57.8%), and it was associated with greater progression of PAV (+0.51% vs +0.23%; p=0.003) and a greater likelihood of undergoing progression of PAV (multivariate adjusted odds ratio 1.25; p=0.01).

The researchers also found that the risk of plaque progression differed depending on which of these five components were present. When the individual components were used in the model instead of metabolic syndrome, hypertriglyceridemia (OR 1.26; p=0.008) and a body-mass index (BMI) of 30 or higher (p=0.05) predicted progression of PAV. "The ones that really stood out in this analysis were obesity and high levels of triglycerides," Nicholls noted.

But after adjustment for its individual components, metabolic syndrome was no longer an independent predictor (p=0.79).

Nevertheless, a diagnosis of the syndrome may be useful, say the researchers, if only for the fact that it highlights a patient with multiple atherogenic risk factors.

In particular, high triglycerides and obesity in these patients provide important targets for potential therapeutic intervention to more effectively reduce cardiovascular risk, they conclude.

Recognition of the metabolic syndrome is highly relevant for prevention efforts at both the individual and population level. A diagnosis of metabolic syndrome "could help motivate patients to make lifestyle changes that prevent progression of the syndrome to diabetes or cardiovascular disease."

Archives of Internal Medicine. March 8, 2010

Bayturan O, Tuzcu M, Lavoie A, et al. The metabolic syndrome, its component risk factors, and progression of atherosclerosis. Arch Intern Med 2010; 170:478-484

Ding EL, Smit AL, Hu FB et al. The metabolic syndrome as a cluster of risk factors: Is the whole greater than the sum of its parts? Arch Intern Med 2010; 170: 484-485.