Genetics offers understanding of diabetes
have been linked to susceptibility to type 2 diabetes, the most
common kind of the disease, which affects up to 135 million people
worldwide.
The findings, by Inês Barroso and colleagues at the University of Cambridge in the UK and reported in the October issue of PLoS Biology (vol 1(1), pp41-54), support the view that genetic predisposition to type 2 diabetes does not originate from a few major genetic defects, but instead from an accumulation of several small genetic variations.
Furthermore, Barroso and colleagues' results suggest that the two main areas affected in diabetes Type 2, insulin secretion by b-cells and insulin action, are differently influenced by genetic and environmental factors. This could be key to better disease prevention.
The researchers studied 71 genes on more than 2000 individuals, trying to correlate gene variations with the appearance of metabolic changes characteristic of diabetes. They found evidence that eight out of the 71 genes analysed were linked to susceptibility to type 2 diabetes.
The results also confirm the genetic complexity behind type 2 diabetes and emphasises the importance of large-scale studies, one of the few ways to identify such a multitude of genes each with a weak effect, a situation that makes their identification problematic.
Diabetes is a chronic metabolic disease, which results from the inability of the body to properly use glucose, the cell's main source of energy. When not converted into energy, glucose accumulates in the blood causing serious damage to the body tissues and organs. Insulin, a hormone produced in the pancreas by specialised cells called beta-cells (b-cells), regulates the level of glucose in the blood and problems with this hormone are associated with diabetes.
Type 2 diabetes results from a combination of defects in both the production of insulin and the body's response to insulin, with tissues becoming resistant to the action of the hormone.
Inês Barroso and colleagues report that in the group of genes they studied most of those associated with susceptibility to diabetes type 2 are related to the function of b-cells and not with insulin function.
This, say the authors, may suggest that the two dysfunctions behind type 2 diabetes are differently affected by environmental and genetic factors, with insulin resistance being mainly induced by causes in the environment while problems with b-cells' insulin secretion are mainly affected by genetic factors.
While the influence of environmental factors, like obesity, lack of exercise and a diet of fast food, has been well documented, the genetic components behind diabetes have proven more elusive.
