The still-in-progress Illinois study, in which researchers are measuring the effects of diet on gene expression in both weanling and geriatric dogs, is described in a paper in the October issue of the Journal of Nutrition. The scientists use their study as an example of how the use of emerging molecular tools, in general, will unlock the functional aspects of the genes being mapped in a variety of genomes.
"Genome sequencing allows us to understand health across animals," said Lawrence B. Schook, a professor of animal sciences and veterinary pathobiology at Illinois. "Dogs, like humans, get diseases associated with lifestyles. Thus not exercising and over-eating can result in obesity and diabetes. Information about human diseases can be used to treat dogs, and understanding dog diseases can be used to treat humans."
The dog-human bond goes deeper than mutual admiration. In a paper published last month in Science, researchers at the Institute for Genomic Research in Maryland scientists reported that their genome map of Shadow reveals 18,473 genes that correspond to the 24,567 annotated human genes. They also noted that the dog's genome had more genetic similarities with humans than does the mouse -- the most-often used mammal for human health studies.
Schook and colleagues say in their paper that the cat-genome map available to date is even more similar to humans genetically than the dog. To date, Schook said, 263 feline and 451 canine genetic diseases have been identified.
Causes for diseases associated with a single gene can be uncovered with current biological techniques, Schook said, but finding the source of diseases associated with multiple genes "is a much more daunting task."
The emergence of mammal genomes provides fundamental gene-placement information, but now researchers are able to pursue functional genomics to unlock the mysteries of RNA and protein expression. Such research, Schook and colleagues write, will enhance our knowledge of metabolism and improve companion animal nutrition and health.
The dog, they say, "may be a very useful model, as many of the most common diseases of purebred dogs are also major health concerns in humans." They cite arthritis, cancer, deafness, heart disease, blindness, epilepsy and chronic metabolic diseases.
In the Illinois study, a diet of mostly high-quality animal-based ingredients is being compared with a mainly plant-based diet. Researchers are analyzing ribonucleic acid (RNA) samples to generate gene expression profiles of some 384 genes associated with metabolism and immune function. They also are monitoring digestion, fetal microbes and concentrations of fermented end products to measure the effects of dietary changes.
Illinois scientists hope the project will identify biomarkers that can predict diabetes, a disease that is appearing among the 40 percent of aging overweight dogs and cats in the United States, and other medical issues.
The general study of metabolic profiles of cells, tissues and organisms is designed to identify molecular markers that reflect nutritional and/or health status. Eventually, Schook said, such studies could result in animal feed that includes functional ingredients to help prevent and treat diseases in general or to target breed-specific genetic problems.
Schook's collaborators are George Fahey, professor of animal sciences, and Kelly Swanson, a postdoctoral fellow in animal sciences. Pyxis Genomics of Chicago supports their research. Schook is a member of the board of directors of the privately held company that focuses on genetic research on natural disease resistance in food animals, preventive medicine for dogs and cats, food safety and security, and human therapeutics.