Lifestyle factors that influence your risk of vascular disease including high blood pressure, obesity, diabetes and smoking also increase your risk of developing dementia, according to a new study from UC Davis.

Researchers from UC Davis looked at data from the Framingham Offspring Cohort Study, a prospective cohort study beginning in 1978. They tracked participants for markers of vascular disease, which are known to be associated with diet and lifestyle choices.

Starting in 1999, researchers started measuring vascular disease in the brain including brain volume and white matter hyperintensities, and also conducting cognitive tests such as verbal and spatial memory and decision making.

Participants with higher blood pressure developed cognitive problems and hyperintensities more quickly. Obesity was highly correlated with increased cognitive decline on executive tasks. Diabetes was associated with decreased volume in a region of the brain called the hippocampus, which is responsible for memory formation. Smokers had a more rapid increase in hyperintensities.

Thus poor lifestyle choices that lead to vascular problems and obesity may also contribute to decline in cognitive health.

Diet sodas increase waist size dramatically. Image courtesy of baileyraeweaver.

In an attempt to cut back on sugar and calories, many people turn to artificially sweetened diet soda to get their fix. However, two new studies suggest that not only does diet soda fail to help people lose weight, it may in fact contribute to weight gain by raising blood sugar and paving the way for type 2 diabetes.

In the first study, participants in the San Antonio Longitudinal Study of Aging (SALSA) were followed for an average of 9.5 years. Researches tracked height, weight, waist circumference and diet soda intake at several points throughout the study.

People who regularly drank diet soda showed an increase in waist circumference of 70% compared to those who did not drink diet soda. Worse, those who drank the most diet soda (more than two servings per day) showed a staggering 500% increase in waist size compared to non-drinkers.

While the biological mechanism by which diet soda may contribute to abdominal fat is still unknown, another study done using mouse that are more prone to diabetes suggests the artificial sweetener aspartame may be to blame. In this study researchers fed the mice food that either did or did not contain aspartame, the no calorie sweetener known commercially as Equal.

The mice fed the aspartame diet developed higher fasting glucose and lower insulin than the control group, indicating that the sweetener may contribute to the development of insulin resistance that could lead to weight gain and ultimately type 2 diabetes.

Both studies were presented at the American Diabetes Association’s Scientific Session conference in San Diego this week. The studies have yet to be subject to peer review.

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The gene CMAH is needed to induce human-like diabetes in mice. Image courtesy of AlicePopkorn.

New research suggests that rodents and other mammals might not be ideal for studying type 2 diabetes because of a gene that was deleted from the human genome millions of years ago.

Virtually all mammals produce specific sugar molecules that aid cells in interacting with their environment. That is, all except humans. Around 2 to 3 million years ago humans lost CMAH, a gene that codes for an enzyme that produces the sugar Neu5Gc.

To test the role of this gene, researches compared two sets of mice. One group had a normal CMAH function and Neu5Gc production, the other group did not—just like humans. Both groups of mice were fed a diet that normally induces obesity and insulin resistance (metabolic syndrome), and both groups experienced these symptoms. However, only the mice missing the CMAH gene had lost the ability to produce insulin in the pancreas.

These findings suggest that while normal mice can exhibit some of the symptoms of type 2 diabetes in the lab, they do not mimic the full effects of metabolic syndrome experienced by humans exposed to a similar diet.

Future diabetes research may be better served using mice with a genetic background more similar to humans and missing the CMAH gene.

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Could a genetic test have told me I was at a higher risk for developing type 2 diabetes? Image source: aldenchadwick

Metabolic syndrome isn’t quite as scary as it sounds.  Basically I am on my way to type 2 diabetes.  But if I eat better and get off the couch, I should stave off the disease and get better.

My question, naturally, is whether or not a genetic test could have told me I was at a higher risk for developing type 2 diabetes.  And whether I would have done anything with that result.

As you know if you’ve been following my blog, I took a 23andMe genetic test and have been writing about it since.  The image below shows what the front page of my clinical report looks like (click to enlarge):

According to the DNA checked in this test, I am in the average risk range for type 2 diabetes.  This doesn’t really seem to line up with my reality.  But I might not expect it to since these genetic tests are so limited right now.

This kind of test can be informative with the yes answer—yes I carry a certain version of a gene that might lead to a disease.  But the no answer isn’t that useful.  It doesn’t mean that they've looked at all the possible genetic differences that can lead to a disease and I don’t have any of them.  Basically it means that they didn’t find the specific genetic difference they were looking for.

Now I wouldn’t necessarily have predicted that any genetic test available right now could tell me a lot more than that.  Type 2 diabetes is too complicated for that and a whole lot more research will need to be done to get a genetic test useful to lots of people.

But still, this is probably what people are looking for with these sorts of genetic tests.  Will I get cancer, type 2 diabetes, Alzheimer’s, Parkinson’s, etc.?  For most of these cases, the tests can tell you a lot about rare forms of these diseases but little about the more common forms.

So the no answer didn’t really help me much.  Here I am on my way to being a diabetic and the test said I was at average risk.  Of course, I suppose I didn’t even need to take a test… all four of my grandparents came down with type 2 diabetes.  Like lots of these complex diseases, family history is the best predictor.

The second part of my question is a hypothetical one.  Let’s say they had a perfect genetic test that said that I was at an increased risk for type 2 diabetes.  Would it have changed my behavior?  I’m not sure but probably not.

I certainly wouldn’t have changed any of my behaviors when I was young.  I was invincible, remember?

Now that I’m a bit older, such a test might have influenced my behavior a bit.  I already knew about my risk because of my grandparents but my thought has always been that maybe I got lucky and didn’t inherit their tendencies towards diabetes.  But if they were tested and we shared the same genetic differences that led to type 2 diabetes, then I might be worried enough to change what I was doing.

Most likely though, my behavior modification wouldn’t be perfect.  What I’d probably do is keep watching TV and eating Twinkies but get my blood sugar tested more often.  Once I was headed for diabetes, then I’d modify my behavior and keep it at bay.  (I’m sure doctors scream into their pillows at night because of patients like me.)

This is different than some people’s reactions to other genetic tests.  For example, some women who find out they have the version of BRCA1 that greatly increases their chances of breast and ovarian cancer have a double mastectomy and/or a hysterectomy before there are any signs of cancer.

I might react much more strongly with a valid cancer genetic test.  Cancer is scary, nasty and not really reversible.  Type 2 diabetes is different.  You can start down the road, modify your behavior and then nip it in the bud.  Carpe diem and then pay the piper.

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