Genetics and Diabetes
Genetics and Diabetes
We have shared information about cell transplantation in these articles. Here is an update. The researchers at the University of California, San Diego, report that a genetically modified line of insulin-producing cells grown in the laboratory have been shown to function successfully when transplanted into mice. They have a long way to go before they can scale up the process to do large animal and hopefully human trials, but they believe they are on the correct track for a cure of type 1 diabetes.
The day I was diagnosed with diabetes at age 41, I looked at our two children and wondered if they would be able to live their lives without the devastation of this disease. Although I knew in my head that the disease was not communicable, I had been treating many type 1 diabetics in an inpatient hospital and outpatient programl. So there I was wondering what the average person may opine when they hear about someone becoming diabetic. After all, my parents knew of no family members who ever had type 1 or 2 diabetes. My answer, after thoughtful reflection, was that they had never lived long enough to get type 2 and that no one in America knew the whole family in the Old Country. From that day, I made sure I researched the genetics of the disease and have continued to follow the news in this area because I am a mom, and because I want my children, if they are at added risk, to be able to forestall or stop the progress of the disease. It is also the reason that we support research for a cure of diabetes. We hope you do too.
In the United States 789,000 people are diagnosed with diabetes every year. As you may know, 90% to 95% of those have type 2 diabetes, which affects those over 40 years of age, is more prevalent in certain ethnic groups, and those who are obese and sedentary. In the US 13,000 new cases of type 1 diabetes are diagnosed each year, making it one of the most common chronic diseases in our country. First we will look at the odds of developing Type 1 diabetes. Here are the facts:
If an immediate relative (parent, sibling, offspring) has type 1 diabetes, your risk is 10 to 20 times the risk of the general population. Your risk can go from 1 in 100 to roughly 1 in 10 or possibly higher, depending on which family member has diabetes and when they developed it.
If one child in a family has type 1 diabetes, their siblings have a 1 in 10 risk of developing it by age 50.
The risk for a child of a parent with type 1 diabetes is lower if it is the mother who has the diabetes rather than the father. If it is the father, the risk is 1 in 10 ( 10 percent) . If it's the mother the risk is 1 in 24 ( 4 percent), and if the mother is over age 25, the risk drops to 1 in 100, the same for the general American population.
If one of the parents developed type 1 diabetes before age 11, their child's risk is somewhat higher than the figures in #3 and somewhat lower, if the parents was diagnosed after age 11.
About 1 in 7 people with type 1 diabetes has a condition known as type 2 polyglandular autoimmune syndrome. In addition to type 1 diabetes, these people have thyroid disease, malfunctioning adrenal glands, and sometimes other immune disorders. For those with this syndrome, the child's risk of having the syndrome, including type 1 diabetes, is 1 in 2 according to the American Diabetes Association.
Caucasians have a higher risk of developing type 1 diabetes than any other race. Whether this is due to difference in environment or genes is unclear. Even in this population, most people who are susceptible do not develop diabetes. One gene which influences the immune system is thought to be HLA-DR. Most Caucasians with diabetes carry alleles (gene variants) 3 and/or 4 of the HLA-DR gene. The HLA-DR7 allele plays a role in diabetes in blacks, while HLA-DR9 allele is important in diabetes among Japanese.
Among Caucasians, the risk of diabetes varies geographically. In general, the risk is higher in Northern Europeans than Southern Europeans. While climate may have a part in this, the fact that there are higher rates in Sardinia which is in the Mediterranean, goes against this theory. In recent decades, there has been an increase of type 1 diabetes in the United States and Europe. While most of Asia has a lower rate of type 1, Japan is also experiencing increased numbers of diagnoses. Since the gene pool does not change that much over one generation, something else must be going on which may be environmental or behavioral. Temporal clusters of type 1 diabetes may be reason to suspect an environmental agent, but today, these are thought to be coincidence, as the autoimmune process leading to diabetes is quite a long process, so that those people who develop the disease may have lived in many different areas when the process began.
Some people have questioned whether a body trauma, like a car crash or a viral infection, like mumps, can trigger the onset of type 1 diabetes. Although, when I became diabetic, I was told that it was precipitated by a viral infection, it is now thought that the process has already begun and that the trauma places more strain on the body to produce needed insulin which can push the body over the edge. There has been much written about the link between Coxsackie virus, which causes meningitis, and whether it triggers type 1 diabetes. To date, this connection remains unclear. Scientists do have clear information that mumps and diabetes are not connected. In a Maryland study even with a decline in the number of mumps cases after the vaccine was introduced. the incidence of type 1 diabetes did not change. Some researchers believe that early diet may have a role. For example, type 1 diabetes is less common in children who have prolonged breast feeding as infants. Some studies have linked cows' milk to diabetes. The final word here is less than final. Researchers seem to feel that if your child is at great risk, you may want to consider prolonged breast feeding with input from your physicians.
Now we will examine the genetic risks of Type 2 Diabetes:
Type 1 and type 2 diabetes are different diseases with very different incidence patterns. The general population's risk for developing type 1 is 1 in 100 before age 70, and one third develop it before age 20. For type 2 diabetes, one out of 9 Americans will develop it, and almost all will become ill in middle age. The Westernized lifestyle of obesity and sedentary behavior is one component of this disease. In the United States, Mexican Americans, blacks, and Native Americans have higher incidences than Caucasians. The disease is less common in these populations in regions where Westernized lifestyle is not common. Clustering of diabetes in families is more easily recognizable for type 2 diabetes than in type 1. If one sibling develops type 2 diabetes, their sibling's risk is doubled (to 1 in 4). If a parent has type 2, one's risk is also double the general population's risk. Although the research is ongoing, it is speculated that if both parents have type 2 diabetes, a child's risk may be as high as 50 percent. While type 2 diabetes may have a genetic basis, it is highly influenced by environmental and behavioral factors. Obesity is a strong factor in type 2, particularly in young adults and those who have been over weight for long periods of time. In fact, a study presented to the ADA annual meeting showed a marked increase in American and Japanese children aged 6 to 19 with type 2 diabetes believed to be linked to Western lifestyle.
In the past we have done an article on MODY, (maturity-onset diabetes of the young) that typically develops in people in their teens and 20s. This runs in families in a pattern which suggests that it hits every generation and every person in that family with MODY had a parent with MODY. Researchers have found six genes that produce MODY, but they only account for diabetes in about one-third of the families. The diabetes in the rest of the families is so far unexplained. Similar patterns can be found in studies of families with the more common form of type 2, only the age of onset differs.
The susceptibility to certain diabetes complications also seems to be linked in some ways with genetics. For people with susceptibly genes for complications, good blood glucose control is still an important mitigating factor. One of the exciting areas of current research is what makes some diabetics more susceptible to complications then others.
Now let's look at how to handle these statistics. Even if we know the risk factors for your child to develop diabetes, do we know the risks for other medical or behavioral problems? And worst case scenario, even if your child does get diabetes, does that have to stop him or her from having a full life? The answer seeems to be a resounding "no". Certainly professional athletes, musicians, doctors and lawyers who have diabetes continue to work to make the world a more pleasant place in which we live. Each month, when I read research in journals, I see first hand the progess that we are making. It is never fast enough or clear enough, but it moves ahead. This would be the place, if this were a web site brought to you by a non profit diabetic association, where we ask you to join and make a contribution. We're not and we don't, but, if you live with diabetes, whether type 1 or 2, you know the daily grind and the fears, the complcations, and the intrusion into our lives. So, dear readers, if you don't have a charity that you support, maybe you want to find one that helps those of us with diabetes -maybe a hospital, research facility, national organization, or a local clinic for the poor. Think about changing your will to include one of these organizations. Write or e-mail you congressman and senator and demand more money for research. These too will help. A few weeks ago the President raised many millions for his party at one dinner party. On the same night Michael J. Fox raised only 2 million for Parkinson's. Why do things like this happen? We all know the simple answer, but we all need to change this type of thinking. All of us with diseases need to make sure that we get the funding necessary for research that will help us and those who will become ill in the future. This article tells us that it will happen, at least for diabetes, and we need to fight to change these statistics.
