A.J. Marian Walhout, PhD, co-director of the Program in Systems Biology and professor of molecular medicine at UMMS, and team described how metabolism and physiology are connected to diet.
Using C. elegans, a transparent roundworm often used as a model organism in genetic studies, Dr. Walhout and colleagues observed how different diets produce differences in gene expression in the worm that can then be linked to crucial physiological changes.
Walhout said, "Worms fed a natural diet of Comamonas bacteria have fewer offspring, live shorter and develop faster compared to worms fed the standard laboratory diet of E. coli bacteria."
Walhout and colleagues identified at least 87 changes in C. elegans gene expression between the two diets. Surprisingly, these changes were independent of the TOR and insulin signaling pathways, gene expression programs typically active in nutritional control. Instead, the changes occur, at least in part, in a regulator that controls molting, a gene program that determines development and growth in the worm.
This connection provided one of the critical links between diet, gene expression and physiology detailed in "Diet-induced Development Acceleration Independent of TOR and Insulin in C. elegans."
Strikingly, Walhout and colleagues observed that even when fed a small amount of the Comamonas bacteria in a diet otherwise comprised of E. coli bacteria, C. elegans exhibited dramatic changes in gene expression and physiology. These results provide the tantalizing possibility that different diets are not "healthy" or "unhealthy" but that specific quantities of certain foods may be optimal under different conditions and for promoting different physiological outcomes.
"It's just as true that a small amount of a 'healthy' food in an otherwise unhealthy diet could elicit a beneficial change in gene expression that could have profound physiological effects," said Walhout.
Additional research by the Walhout Lab further explored the possibility of using C. elegans as a model system to answer complex questions about disease and dietary treatment in humans.
Detailed in the "Integration of Metabolic and Gene Regulatory Networks Modulates the C. elegans Dietary Response," Walhout and colleagues found that disrupting gene expression involved with C. elegans metabolism lead to metabolic imbalances that interfered with the animal's dietary response; a result that may have a direct correlation to the treatment of a class of human genetic diseases.
According to Dr. Walhout, it may be possible to use this genetic regulatory network in C. elegans to compare how certain dietary regimens can be used to mitigate these metabolic diseases. It may also be used to screen for drugs or other small molecules that can produce the same results as dietary treatments.
Though Walhout and colleagues started out asking a fundamental dietary question in the worm, what they got was an answer directly related to disease and treatment in humans, thus establishing C. elegans as a model system for elucidating the mechanisms for dietary responses, inborn metabolic diseases and the connections between them.
The findings are described in a pair of papers published in Cell.