As some of my readers from WAY back (all two of you, hi guys!) may know, diabetes is one of Sci’s favorite things. It’s one of those things that, if she could start her entire little sciency life over, would be something she would heavily consider as a focus. Heck, there’s always another post-doc, right?
Anyway, you might think that diabetes would not be one of the things generally discussed at Society for Neuroscience meetings. But you would be wrong. The symptoms of diabetes, type I or II, stem from not enough insulin, whether that is because you don’t produce any (type I) or you don’t have enough and aren’t sensitive enough to what you have (type II). Insulin isn’t just limited to the gut, pancreas, and muscles, however. It’s also important in the brain. Normally, your brain is pretty responsive to blood levels of glucose, no matter what, because you want your brain to be the last thing to go when your blood sugar levels drop. But insulin still plays an important role, and insensitivity to insulin, like that seen with type II diabetes extends to the brain as well.
This study taught Sci a lot of things that she didn’t necessarily know. First, it taught her that insulin sensitivity is affected by free fatty acid levels. And it taught her that both of these together could have major effects on cognitive impairment. Suddenly the major increases in type II diabetes are looking a little more scary.
V. E. COTERO, E. C. MCNAY “Effect of intrahippocampal FAs with varied saturations on spatial memory in adult Sprague-Dawley rats”
Doesn’t sound like anything to do with type II diabetes, does it? You would be surprised.
Type II diabetes can be induced in rats using a high-fat diet-induced obesity model.
(Fat rats are exceptionally adorable)
The animals show all the symptoms of type II diabetes, and respond to treatments for type II diabetes just like humans do, making them a very good model indeed. What the scientists in this study wanted to look at, however, was not just the physical issues with this disease. They wanted to look at the cognitive effects. It’s not very well publicized, but type II diabetes is not only associated with insulin resistance and weight problems, it’s associated with cognitive declines. The question is, why?
In this study, the authors looked at the relationship between insulin resistance, fatty acids, and spatial memory in an area of the brain called the hippocampus (Greek for seahorse because it’s all curly-like), an area strongly associated with memory. They found before that a high fat diet, with a lot of free fatty acids hanging around, increases insulin-resistance in the hippocampus, and saturated fatty acids have been shown to be associated with aspects of cognitive decline. In particular, fatty acids can change neuronal activity in the hippocampus, which might be responsible for some of the issues they cause. So here, the authors injected fatty acid solutions, either saturated or unsaturated, into the rat hippocampus, and determined the behavioral effects on memory.
(Can we all take a moment to be totally mind-boggled that a single injection of something extracted from olive oil into your brain can completely change behavior?! Srsly…thinking about this too hard boggles Sci’s mind in a major way, and I DO stuff like this all the time!!!)
The authors found that the TYPE of fatty acid made a big difference in how well rats did in a series of mazes. If they used oleic acid in the hippocampus, an unsaturated fatty acid found in olive oil, the rats did BETTER in the maze. If they used palmitic acid, a saturated fatty acid from palm oil, the rats did significantly worse in the maze, indicating that increases in saturated fatty acids in the brain can impair memory function. And the palmitic acid inhibited many of the neurotransmitter changes associated with successful maze completion, suggesting that high fatty acids levels can impair maze performance by inhibiting neuronal function.
This could mean that insulin and saturated fatty acid levels could interact (as found in their previous work), and that the high saturated fatty acid levels could be partially responsible for some of the cognitive declines seen in people with type II diabetes. This could give us other options for treatment of type II, treating not just the endocrine aspects of the disease, but possibly allowing us to find ways to treat the cognitive effects. Also, it’s another great excuse to use more olive oil in your cooking.