Summary

People with diabetes have an increased risk of heart disease. A study now reveals that a specific gene variant can double the risk. When combined with poor glycemic control, the gene variant increases the risk of heart disease four times.

Introduction

Diabetes is known to be one of the most potent risk factors in heart disease. People with diabetes have a two to four times higher risk of getting coronary artery disease (CAD) than those without diabetes. It is also known that various genetic factors play a role in heart disease risk. Recently a gene on a region of chromosome 9 known 9p21 has been implicated with those with a specific variant of this gene running an increased risk. But nothing is known of what the 9p21 gene variant does in diabetes.

What was done

Researchers at the Joslin Diabetes Center, Harvard Medical School and elsewhere studied a group of 734 people with type 2 diabetes of whom 322 had been diagnosed with heart disease. The second study involved a group of 475 type 2 diabetics whose survival status was monitored. Readings of hemoglobin A1C - a measure of glycemic control - in the years before the study were recorded for all participants. They were also tested for the presence of the 9p21 gene variant.

What was found

Participants who had inherited two copies of the 9p21 gene variant - one from each parent - but had good glycemic control had double the risk of CAD compared to patients without the gene variant. When participants had both two copies of the gene variant and poor glycemic control, this risk went up to four fold. There was also a link between death rate at ten years, in the survival study, and the 9p21 variant and poor glycemic control.

What this study means

This study highlights the importance of gene-environment interactions. If the pathway that the 9p21 gene influences is discovered, then it may be possible to better understand the pathology of heart disease and how poor glycemic control contributes. In the meantime, diabetics with the 9p21 gene variant - should a test for it become available - might benefit from tightening their glycemic control in terms of reduced CAD risk.