It doesn't directly contradict the paper you linked, but figured it's worth mentioning - the hypothesis about a diabetes-Alzheimer's link might have originally stemmed from fraudulent work. From the "related story" at the bottom of the linked Science article about fraud https://www.science.org/content/article/potential-fabricatio... (related story is titled "Research backing experimental Alzheimer’s drug was first target of suspicion", also available in their reader here:
https://www.science.org/doi/full/10.1126/science.ade0181?ado...)
> The most influential Cassava-related paper appeared in The Journal of Clinical Investigation in 2012. The authors—including Wang; Arnold; David Bennett, who leads a brain-tissue bank at Rush University; and his Rush colleague, neuroscientist Zoe Arvanitakis—linked insulin resistance to Alzheimer’s and the formation of amyloid plaques. Cassava scientists say Simufilam lessens insulin resistance. They relied on a method in which dead brain tissue, frozen for a decade and then partially thawed and chopped, purportedly generates chemical signals.
> Schrag and others say it contradicts basic neurobiology. Schrag adds that he could find no evidence that other investigators have replicated that result. (None of the authors agreed to be interviewed for this article.)
> That paper supported the science behind Simufilam, Schrag says, “and spawned an entire field of research in Alzheimer’s, ‘diabetes of the brain.’” It has been cited more than 1500 times. Schrag sent the journal’s editor his analysis of more than 15 suspect images in two groups. The editor says the journal analyzed high-resolution versions of the images in the first group. It could not corroborate his findings and therefore did not investigate further.
> The most influential Cassava-related paper appeared in The Journal of Clinical Investigation in 2012. The authors—including Wang; Arnold; David Bennett, who leads a brain-tissue bank at Rush University; and his Rush colleague, neuroscientist Zoe Arvanitakis—linked insulin resistance to Alzheimer’s and the formation of amyloid plaques. Cassava scientists say Simufilam lessens insulin resistance. They relied on a method in which dead brain tissue, frozen for a decade and then partially thawed and chopped, purportedly generates chemical signals.
> Schrag and others say it contradicts basic neurobiology. Schrag adds that he could find no evidence that other investigators have replicated that result. (None of the authors agreed to be interviewed for this article.)
> That paper supported the science behind Simufilam, Schrag says, “and spawned an entire field of research in Alzheimer’s, ‘diabetes of the brain.’” It has been cited more than 1500 times. Schrag sent the journal’s editor his analysis of more than 15 suspect images in two groups. The editor says the journal analyzed high-resolution versions of the images in the first group. It could not corroborate his findings and therefore did not investigate further.