Summary

Higher concentrations of oxidized low-density lipoprotein are linked to the metabolic syndrome. This adds a new factor to this cluster of risk factors, including raised glucose levels and abdominal obesity, which is known to increase the risk of diabetes.

Introduction

Metabolic syndrome is a cluster of risk factors including raised cholesterol, raised blood pressure, and obesity, which is linked to an increased risk of type 2 diabetes and death from heart disease. Findings from the Third National Health and Nutrition Examination showed that the prevalence of metabolic syndrome is nearly seven percent among those in the 20 to 29 year age group and is around 44 percent in those aged between 60 and 69 years. In other words, the risk of metabolic syndrome goes up with age.

It would be useful to have some kind of 'marker' for metabolic syndrome so that those who at risk can be identified at an early stage. One candidate marker is oxidized low-density lipoprotein (LDL, the 'bad' form of cholesterol). The oxidized form is actually just a minor fraction of LDL; it is only 0.001 percent of LDL in healthy people but is as much as five percent in patients who have had a heart attack, which suggests it may play a pathological role. Accordingly, a team at the Catholic University, Leuven, Belgium, has looked at how oxidized LDL relates to the metabolic syndrome.

What was done

This research was a part of the Cardiovascular Risk Development in Young Adults (CARDIA) study which involves over 5,000 men and women aged between 18 and 30 at the start and based in the United States. In the fifteenth year of this study, oxidized LDL was assessed in a sub-group of the study. Metabolic syndrome factors like blood pressure, weight and cholesterol profile were measured and reported for nearly 2,000 participants.

What was found

Oxidized LDL was found to have a direct relationship with the metabolic syndrome. Those who had the highest levels of oxidized LDL were 3.5 times more likely to have metabolic syndrome than those with the lowest levels. A similar relationship was found between oxidized LDL levels and the components of metabolic syndrome - namely, abdominal obesity, elevated glucose and elevated triglycerides.

What this study means

Oxidized LDL is already believed to play a role in blocking the arteries, setting the scene for heart disease. It does not occur naturally, because it is usually prevented by the presence of antioxidants in the blood. Its presence can be detected by a lab test which was done in this study. The link between oxidized LDL and metabolic syndrome, and its components, may not be causal, the researchers say. However, further investigation may show that oxidized LDL is indeed a biomarker for metabolic syndrome. If this is so, then this early indicator may pinpoint those at risk of diabetes through metabolic syndrome, so they can prevent the disease with medication and lifestyle changes.