S-adenosylmethionine (SAMe) and cognitive dysfunction in dogs (Sponsored by Virbac Animal Health)


S-adenosylmethionine (SAMe) and cognitive dysfunction in dogs (Sponsored by Virbac Animal Health)

A roundtable discussion

Pets and people

Landsberg: Dogs have been used as models for aging in people for about 15 years. Dogs do not get Alzheimer's disease per se; but they do undergo brain changes similar to the early changes in Alzheimer's disease. Using neuropsychological tests, researchers have found memory and learning deficits beginning as young as 6 years of age.

Researchers have also examined the brains of older animals and have found increasing ventricular size, neuronal loss, and an increasing beta-amyloid deposition.2 How does that correlate with your knowledge of changes in the brains of people with Alzheimer's?

"Management of dementia is dependent on early detection and intervention."- Dr. Teodoro Bottiglieri
Dr. Teodoro Bottiglieri: In human medicine, the term dementia comprises many different types of cognitive dysfunction. The most common form is Alzheimer's type dementia, which makes up 70% of all cases. The pathologic hallmark of this form of dementia is the deposition of beta-amyloid protein in the brain, which leads to the formation of senile plaques. Studies in dogs have shown that beta-amyloid protein and plaques are present in the brain and as in humans the amount of beta-amyloid burden is correlated with the degree of cognitive decline. The second most common form of dementia in humans is vascular dementia occurring in about 17% of all cases. In aged dogs cerebral vascular changes can also be present.

Landsberg: Dogs do not progress to the full Alzheimer's changes and don't develop such irreversible or major changes like people do. That's why they are used as models for early Alzheimer's changes and why therapeutics might be more effective in animals.

Numerous vascular changes have been identified as well. A couple of the therapeutics available in Europe for dogs are directed at treating blood flow changes in the brain.

Table 1. Most common clinical signs of cognitive dysfunction at baseline
Dr. David Mischoulon: It is striking how similar the presenting clinical signs are for cognitive dysfunction in dogs and people. In people, we see a lot of the same problems with sleep abnormalities, changes in activity, and disorientation. We also note a couple of differences. First, soiling is usually not a problem in Alzheimer's patients until very late in the disease. Second, people have a tremendous capacity for denial, which a dog doesn't have. The dog cannot deliberately try to hide its deficits, compensate for them, or argue with you when you tell them something is wrong. Sometimes it is hard to convince families that this is a dementia and requires treatment. Are dog owners prone to denial when they start seeing problems in their pets?

Table 2. Study results: Improvement in total mental score and geriatric disability index as measured on Day 60
Florsheim: Many are and some don't bring up problems with their veterinarian because they think the pet is just getting older.

Landsberg: If we can get owners to understand the disease process, the signs to look for, and the fact that therapies exist, they might volunteer the information much earlier.

Mischoulon: With people, the fact that we now have treatments for Alzheimer's disease that can alter the course of the illness is a strong incentive for people to open up. People are more likely to admit a problem exists if they know something can be done.