May 1, 2008 - Health + Traits

Genetic Factors Related to Blood Glucose

istock_000002904128xsmall.jpgThe amount of sugar in the bloodstream must be tightly controlled. Too much can cause damage to nerves, blood vessels and organs. But too little sugar starves the body, especially the brain, of the energy it needs.

Fasting plasma glucose (FPG) levels are a measure of how well a person’s body can control blood sugar levels, a process that goes awry in diabetes. A report published online today in Science Express finds that FPG levels can be impacted by single-letter variations in genes known to be involved in blood sugar regulation.

Blood Sugar Levels

Physicians routinely test their patients’ FPG levels to screen for diabetes and pre-diabetes. A high blood concentration of glucose after 8 to 10 hours of fasting indicates that a person’s ability to regulate blood sugar is impaired. High FPG levels are also associated with coronary heart disease mortality for both diabetic and non-diabetic individuals.

In order to identify genetic variants involved in blood sugar control, Nabila Bouatia-Naji and colleagues carried out a genome-wide association study to find single-nucleotide polymorphisms, or SNPs, correlated with FPG levels.

The most strongly associated SNP in an initial sample of about 650 non-obese French people. The same SNP was correlated with FPG levels in a second sample that included about 3,400 French people, approximately 5,000 Finns and a group of about 860 obese French children.

Additional Variants

Two other SNPs that were previously found to be associated with FPG were also found to be significantly associated with FPG levels in this study. The researchers believe that these genes affected by these SNPs affect the threshold level of glucose in the bloodstream, which triggers the secretion of insulin by the pancreas. The higher the threshold, the higher the blood glucose level will rise before insulin starts to regulate it.

“These sequences explain about 5 percent of the normal variation in blood glucose levels between otherwise healthy people,” explained Robert Sladek, one of the study’s senior authors.

When all three SNPs were considered together to create a score (each person has two copies of each SNP and gets one point for each “low FPG” version, meaning the score can range from 0 to 6), the researchers found that on average people who scored a 5 or 6 had FGP levels 0.24 mmol/l lower than people who scored 0 or 1.

“It’s important to know that a high blood glucose level, even within the normal and non-diabetic range, is a risk factor for early mortality,” said Dr. Philippe Froguel of Imperial College and CNRS. “Epidemiological studies have shown that 80 percent of the risk of cardiovascular disease is related to a blood glucose level just above the average.” The researchers propose that the three SNPs they identified “are likely to have a non-negligible impact on human health.”


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