Conjugated linoleic acid prevents inflammatory damage resulting from immune response

One of the isomers of conjugated linoleic acid, a group of fatty acids found in milk, is a natural regulator of the COX-2 protein, which plays a significant role in inflammatory disease such as arthritis and cancer, according to a study published by University of Wisconsin-Madison researchers.

"It's clear from previous research that conjugated linoleic acid, or CLA, prevents inflammatory damage resulting from immune response," says Mark Cook, a professor of animal science in UW-Madison's College of Agricultural and Life Sciences. "We've identified the biochemical mechanism by which this occurs."

CLA, which is synthesized by microbial fermentation in the rumen of dairy cows, exists naturally in a number of structural forms. Cook's team determined that one of the variants inhibits the COX-2 protein by blocking a key cellular pathway. The COX-2 protein is known to play a significant role in many inflammatory diseases and is an important drug target for treating arthritis and cancer, Cook says.

While the amount of the anti-inflammatory isomer of CLA in milk is small relative to other fatty acids in milk, there may still be enough to elicit an effect if someone consumes dairy products every day, says Cook. He is planning a study, in collaboration with researchers in the dairy science and food science departments, to determine whether the amount of anti-inflammatory CLA in milk can be increased by changing dairy cow diets.

A poultry scientist, Cook's interest in CLA arose when he began to investigate what seemed at first to be a simple question: Why does a chick or any other animal raised in a germ-free environment grow faster than one raised in a conventional environment?

"In animal agriculture, you can see as much as a five to ten percent difference in weight at a given age in a growing animal because a secondary effect of immune response is that it suppresses growth," Cook says. The immune system protects the body by fighting disease, but the defense comes at a price, Cook says, including inflammation, muscle wasting and loss of appetite.

"Conventional wisdom dictates that you can increase growth by treating the animal with antibiotics to kill bacteria and avoid activating the immune defense system, but this raises long-term concerns about developing antibiotic resistance," he adds. "You can also suppress the animal's immune system, but that makes it much more susceptible to disease."

However, Cook is interested in another approach: Using CLA as a natural way to prevent "collateral damage" from the immune system's response to invading pathogens. "The ideal solution is to let the immune system fight bacteria, but at the same time to maintain the overall health of the system," he says.

Cook is one of many UW-Madison researchers who are interested in the health benefits of CLA. Others include Michael Pariza, director of the Food Research Institute and chair of the food microbiology and toxicology department; James Ntambi of the biochemistry department; and Dale Schoeller of the nutritional sciences department.

His collaborators on the recent study include Guangming Li, a postdoctoral fellow in animal sciences; David Barnes, a former assistant professor of animal sciences; Daniel Butz, a former research associate in nutritional sciences; and Dale Bjorling, a professor of surgical sciences.