Insulin Resistance may cause Alzheimer's

Chris Masterjohn recently posted a couple of fascinating abstracts that proposed a relationship between high-carbohydrate diets, insulin resistance and Alzheimer's Disease on Native Nutrition.

The first abstract said that a specific variant of a gene called E4 is rare among populations with a long history of agriculture. According to the authors, this implies that individuals with E4, which was more common in pre-agricultural populations, were at a disadvantage when consuming the high carbohydrate diets that agriculture produces. Over time, this lead to a rarity of E4 in the groups that had high carbohydrate diets.

It is also known that those with E4 are at a higher risk of getting late onset Alzheimer's Disease, and that E4 has a similar effect as high carbohydrate diets on lipid (e.g. fatty acid) metabolism. The authors propose that the cause of Alzheimer's Disease can be explained by this similarity, and that one of the ways this is happening is due to elevated levels of insulin causing damage to neurons in the brain.

In conclusion, they state:

A change in diet emphasizing decreasing dietary
carbohydrates and increasing essential fatty acids (EFA) may effectively prevent Alzheimer's Disease. Interventions that restore lipid homeostasis may treat the disease, including drugs that increase fatty acid metabolism, EFA repletion therapy, and ketone body treatment.

The second abstract cites epidemiological research showing that insulin resistance increases the risk of developing Alzheimer's. By studying the effects of creating insulin resistance in mice that were genetically prone to Alzheimer-like brain disease, they conclude:

Our study is consistent with the hypothesis that insulin resistance may be an underlying mechanism responsible for the observed increased relative risk for AD neuropathology

There is an enlightening transcript of a lecture by Dr Ron Rosedale on Mercola's website, Insulin and Its Metabolic Effects, that explains the workings of insulin on your body's cells. According to Rosedale, all age-related diseases like heart disease, cancer and even the effects of aging itself have their roots in cellular signalling, and insulin plays a primary role. What he describes seems consistent with the insulin-Alzheimer's theory proposed in the studies above (e.g. the 3rd part of his transcript on glycation).