Bad news, fructose alters hundreds of brain genes
Got a sweet tooth? Maybe you even have some sugary goodness with you right now… as you are reading this. Well you may want to put that down.We know a range of diseases — from diabetes to cardiovascular disease, and from Alzheimer’s disease to attention deficit hyperactivity disorder — are linked to changes to genes in the brain. Unfortunately for those who love their pop tarts, a new study has found that hundreds of those genes can be damaged by fructose, a sugar that’s common in the Western diet, in a way that could lead to those diseases.
All is not lost however, the researchers discovered good news as well: An omega-3 fatty acid known as docosahexaenoic acid, or DHA, seems to reverse the harmful changes produced by fructose. But you should probably finish reading before you get your hopes up.
“DHA changes not just one or two genes; it seems to push the entire gene pattern back to normal, which is remarkable,” said Xia Yang, a senior author of the study and a UCLA assistant professor of integrative biology and physiology.
“And we can see why it has such a powerful effect.”
DHA occurs naturally in the membranes of our brain cells, but not in a large enough quantity to help fight diseases.
“The brain and the body are deficient in the machinery to make DHA; it has to come through our diet,” said Fernando Gomez-Pinilla, a UCLA professor of neurosurgery and of integrative biology and physiology, and co-senior author of the paper.
DHA strengthens synapses in the brain and enhances learning and memory. It is abundant in wild salmon (but not in farmed salmon due to differences in diet) and, to a lesser extent, in other fish and fish oil, as well as walnuts, flaxseed, and fruits and vegetables, basically all the stuff that most people don’t enjoy eating.
Americans get most of their fructose in foods that are sweetened with high-fructose corn syrup, an inexpensive liquid sweetener made from corn starch, and from sweetened drinks, syrups, honey and desserts. The Department of Agriculture estimates that Americans consumed an average of about 27 pounds of high-fructose corn syrup in 2014.
It isn’t the devil however, fructose is also found is in most baby food and in fruit, although the fiber in fruit substantially slows the body’s absorption of the sugar — and fruit contains other healthy components that protect the brain and body, which is why that pop tart is a no, but that apple is a yes.
To test the effects of fructose and DHA, the researchers trained rats to escape from a maze, and then randomly divided the animals into three groups. For the next six weeks, one group of rats drank water with an amount of fructose that would be roughly equivalent to a person drinking a liter of soda per day. The second group was given fructose water and a diet rich in DHA. The third received water without fructose and no DHA.
After the six weeks, the rats were put through the maze again. The animals that had been given only the fructose navigated the maze about half as fast than the rats that drank only water — indicating that the fructose diet had impaired their memory. The rats that had been given fructose and DHA, however, showed very similar results to those that only drank water — which strongly suggests that the DHA eliminated fructose’s harmful effects.
Other tests on the rats revealed more major differences, the rats receiving a high-fructose diet had much higher blood glucose, triglycerides and insulin levels than the other two groups. Those results are significant because in humans, elevated glucose, triglycerides and insulin are linked to obesity, diabetes and many other diseases.
However, it didn’t stop there, the research team sequenced more than 20,000 genes in the rats’ brains, and identified more than 700 genes in the hypothalamus (the brain’s major metabolic control center) and more than 200 genes in the hippocampus (which helps regulate learning and memory) that were altered by the fructose.
From the altered genes they identified, the vast majority of which are comparable to genes in humans and are among those that interact to regulate metabolism, cell communication and inflammation. Among the conditions that can be caused by alterations to those genes are Parkinson’s disease, depression, bipolar disorder, and other brain diseases.
“Of the 900 genes they identified, the researchers found that two in particular, called Bgn and Fmod, appear to be among the first genes in the brain that are affected by fructose. Once those genes are altered, they can set off a cascade effect that eventually alters hundreds of others,” Yang said.
The research also uncovered new details about the mechanism fructose uses to disrupt genes. The scientists found that fructose removes or adds a biochemical group to cytosine, one of the four nucleotides that make up DNA. (And for those rusty with biology — shame, shame — the others are adenine, thymine and guanine.) This type of modification plays a critical role in turning genes “on” or “off.”
Although DHA appears to be quite beneficial, it is not a magic bullet for curing diseases. Additional research will be needed to determine the extent of its ability to reverse damage to human genes.
Meng, Q., Ying, Z., Noble, E., Zhao, Y., Agrawal, R., Mikhail, A., Zhuang, Y., Tyagi, E., Zhang, Q., Lee, J., Morselli, M., Orozco, L., Guo, W., Kilts, T., Zhu, J., Zhang, B., Pellegrini, M., Xiao, X., Young, M., Gomez-Pinilla, F., & Yang, X. (2016). Systems Nutrigenomics Reveals Brain Gene Networks Linking Metabolic and Brain Disorders EBioMedicine DOI: 10.1016/j.ebiom.2016.04.008