A High-Salt Diet Causes Dementia in Mice
Sanjena Venkatesh ‘21
A new study from the Cornell Weill Medical School has found a striking correlation between high-salt diets and dementia in mice.
Figure 1: Mice on high-salt diets developed dementia and reduced blood flow to the brain. (Image Source: Wikimedia Commons)
For years, scientists have investigated various potential causes of dementia, such as high-salt diets. In humans, though, the effects of salt on cognition were simply attributed to hypertension. However, a new study shows a more direct relationship between dementia and salt intake (2).
The research team, led by Dr. Faraco of Weill’s Department of Radiology, analyzed the cognition of mice following changes in salt intake. These mice were placed on diets of 4 percent or 8 percent salt, which represents an eight to sixteen-fold increase in salt as compared to the diets of normal mice. After eight weeks, MRI scans illustrated drastically reduced blood flow to areas of the brain associated with learning and memory (2). This was due to the inability of endothelial cells to reduce production of nitric oxide – a gas that relaxes blood vessels to increase blood flow. Interestingly, the results were reversible: following four weeks on a regular diet, these functions returned to normal (2).
The mice on these high-salt diets developed dementia. In fact, they performed drastically worse on the object recognition test, maze test, and nest building (3). To understand the underlying biological connection between salt and cognition, scientists conducted a number of experiments. They found that in response to high salt levels, the mice developed an adaptive immune response in the gut with increased activity of T helper lymphocytes (TH17). These white blood cells boosted production of interleukin-17 (IL-17), a protein that regulates immune and inflammatory responses. The resulting increased circulation in IL-17 gives way to “endothelial dysfunction and cognitive impairment” (2).
Ultimately, the aim is to prevent or find a cure for dementia. Recent research suggests the IL-17-Rock pathway, which reduces circulating levels of IL-17, will open the door to many possibilities. According to Dr. Faraco , “It appears to counteract the cerebrovascular and cognitive effects of a high-salt diet, and it also may benefit people with diseases and conditions associated with elevated IL-17 levels, such as multiple sclerosis, rheumatoid arthritis, inflammatory bowel disease, and other autoimmune diseases” (3).
References
- What is dementia? (2017, May 17). Retrieved from https://www.nia.nih.gov/health/what-dementia
- Faraco, Giuseppe, et al. (2018, January 15). Dietary Salt Promotes Neurovascular and Cognitive Dysfunction through a Gut-Initiated TH17 Response. Nature News. Retrieved January 29, 2018 from nature.com/articles/s41593-017-0059-z
- Weill Cornell Medicine. (2018, January 16). A high-salt diet produces dementia in mice. ScienceDaily. Retrieved January 29, 2018 from www.sciencedaily.com/releases/2018/01/180116131306.htm