"This was one of those lucky accidents, the way science is supposed to happen." So reminisced biochemist/pathologist D. Larry Sparks, senior scientist at the Sun Health Research Institute in Tucson, Ariz.
"Back in 1986," he recounted, "when I was doing autopsies elsewhere, we found that people with coronary artery disease [CAD] had Alzheimer's disease [AD] plaques in their brains identical to what's seen in patients. So I figured: Cholesterol must be the main player in CAD. So instead of hunting for a CAD animal model, I looked for one with heart disease for AD pathology. And lo and behold, a rabbit fed on a cholesterol diet was exactly where we found about ten different features of AD in their brains."
Fast forward to more modern times. "When I came out to Sun City with the animal studies being done here," Sparks continued, "cholesterol didn't induce anything in AD anymore. I went down to the animal vivarium. First thing, I walked in the door and asked, What are those blue bottles lining the wall?' The lab technicians said, That's the distilled water we give those rabbits.'
"So I said, Okay, now I want to do those animal studies over again, and this time give half the rabbits distilled water from those blue bottles, and half tap water from the faucet.' Guess what? Cholesterol caused cardiovascular disease in those rabbits."
Sparks is lead author of a paper in the current Proceedings of the National Academy of Sciences (PNAS). Its title: "Trace amounts of copper in water induce b-amyloid plaques and learning deficits in a rabbit model of Alzheimer's disease."
"I think our finding lends credence to the fact," Sparks told BioWorld Today, "that copper may be a player in Alzheimer's disease. We don't know if the copper acts without the nidus of cholesterol-induced alpha-beta production. The basic premise," he explained, "is that the cholesterol induces that plaque-forming production, and the copper shuttles it either in or out of the brain. That's a two-step process. If we put the copper in, it attenuates the clearance of the over-produced alpha-beta and makes it accumulate in the brain. In the animals given distilled water, the cholesterol in their diet induces overproduction of alpha-beta - but it's clear in their blood."
Sparks pursued his scenario: "The distilled water doesn't have copper in it. We were able to demonstrate that the animals that didn't have elevated cholesterol in the brain had elevated alpha-beta in their blood. That's the distilled water. And the animals on tap water had only very little increments in the blood - clearly suggesting inhibited clearance."
Fat-Rich Diet, Brain To Blood
"If I had a cholesterol-rich diet in both animals, and copper in only one of them, the animals on distilled water would get only a little alpha-beta in the brain, but twice as much in the blood. Those rabbits demonstrate an 80 percent memory deficit - a decline in AD cognition. We administered an eye-blink test," he went on. "Eye-blink is the only behavioral test in animals that has ever been used in many people - that is, non-communicative AD patients. We use an eye-blink as a means to communicate. In the test," Sparks recounted, "there's an audible tone that lets the animal know it's immediately followed by a puff of air in the eyes that he should blink to avoid.
"Some people say it's a conditioned response, but in the very short period of time between tone and puff, the hippocampally based memory acquisition affects memory in the neuronal plaques. But these rabbits can hear the tone all the same. It's only when we shorten this time down so it's temporal-lobe hippocampally based that these animals show that 80 percent AD-like memory deficit.
"And in the hippocampus," Sparks said, "we're showing plaque-like deposition that is positive for thioflavin [a dye marker for amyloid]. They have a regional distribution in the rabbits, exactly the same as we see in those AD patients, more in the temporal lobe of the hippocampus than in the superior parietal. But there's this glaring overlap of pathology, both structural and functional, with regard to neuropathology and behavioral deficits between the cholesterol-fed rabbits, which were able to induce in 70 days compared to Alzheimer's patients who have the same pathology, and the cardinal feature is memory deficits - which may take 70 years."
Stockpile Cholesterol To Shuttle It
"Our rabbits tend to gain weight but tended to lose a little bit of it at the end of the experiment. We know the systemic organs of cholesterol-fed animals tend to get larger. They accumulate cholesterol as a means by which to shuttle it, because they can't get rid of all they've got. So they send it to other places - just like in human disease. Between animals and humans it would suggest that a simple lifestyle change could be of some benefit to people with AD in drinking purified water. It only makes intuitive sense," he added, "the cleaner the water you drink, the better it's going to be."
His institute's sponsoring entity recently advised that it is renewing its funding for another three years. Thus supported, Sparks and his co-authors recounted, "We'll see if we can get the animals going for a little while, then take them off the copper and try to prove the fact that the copper is involved in the transport or clearance of the beta-amyloid. And we're approaching a number of entities at this time to see if we can do a proof-of-concept clinical trial of individuals with mild AD.
"We've pitched our protocol for this project with our two concerns - institute and industry - and both are positively inclined. I'm hoping that with the next year we will do a single-site trial enrolling 60 patients. I'm pushing for a randomization trial."
He will be looking at blood-borne markers. "If on the off chance we see some clinical benefit - a change in the slope of the progression of the disorder - then that would be evidence," Sparks concluded, "toward undertaking a large multicenter trial."