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Specially bred rodents in demand as US obesity research booms

WILMINGTON -- Scientists usually pick up lab rats by their tails. But a new breed used in obesity research grows so heavy that researchers lift the rats by their bellies so their tails don't pull off.

 

"They're couch potatoes," said Dan Spada, a supervisor at Charles River Laboratories International Inc., showing a visitor a few of the docile rats the company hopes to sell by the thousands.Known as the JCR, after the initials of its Canadian developer, the rat is an all-American breed for scientists. Public health officials report epidemic rates of heart disease, diabetes, and other health problems across the United States stemming from a population bulking up on a fast-food diet and a sedentary lifestyle.

In response, companies and academic institutions are clamoring for research models to use in a booming study area. The National Institutes of Health expects to distribute $332 million for obesity research next year, up from $297 million in 2002, and even more in related areas like diabetes. The agency wants scientists to find out where the pounds come from. The conventional wisdom, that obesity is caused by too much eating and too little activity, doesn't explain why some people get fat and others don't.

Enter the heavy rodents. Researchers examining the causes or effects of obesity can buy normal lab rats for $20 apiece and fatten them up with high-lard diets, but that might not generate the characteristics being studied. Many companies prefer to buy specialized rats like the JCR, whose prices start at $146.30 for a six-week-old female, and go up about $12 for each week of age.

The rats' life expectancy is less than half the normal three years. Some get heart attacks just from the stress of moving into new cages. Predisposed to become obese on any diet, some grow to be 2.5 pounds, several times the average, nearly paralyzed by the rolls of fat around their abdomens.

"Using these animals, we can more quickly determine if a product is effective in treating obesity-related problems," said James Komorowski, vice president at Nutrition 21 Inc., a Purchase, N.Y., company that has bought hundreds of JCRs to test diet supplements.

Other customers don't want to devote the time and resources it takes to raise research subjects.

"We're tending to run out of animal space ourselves," said Jeffrey S. Flier, chief academic officer at Beth Israel Deaconess Medical Center. He keeps a colony of thousands of mice to study how fat cells release hormones that lead to diabetes, but is exploring whether to buy pre-fattened mice from outsiders at $85 a nose.

Suppliers of the overweight animals say the area was a backwater until recently. Now they're rushing out new strains through genetic engineering or selective breeding. In Bar Harbor, Maine, executives at the nonprofit mouse provider Jackson Laboratory say an unprecedented seven companies have signed up to buy a new mouse it bred that becomes moderately obese and develop diabetes late in life -- a useful model for testing drugs to prevent the disease.

"We're seeing an increased interest in diabetes and obesity models, and if you pick up a newspaper you know why," said Jackson vice president Susie Airhart.

At Charles River, the world's largest supplier of rats and mice for biomedical research, executives say demand makes the obesity-research sector one of its fastest-growing.

"It's huge, pardon the pun," said Terrence F. Fisher, a company product manager.

Animal research models accounted for 40 percent of the company's revenue of $555 million last year, with the remainder from the services it provides to biotechnology and pharmaceutical companies, such as testing the safety and effectiveness of drugs. The company won't quantify exactly how many animals it sells a year, but by way of comparison, its nonprofit competitor Jackson Laboratory took in $46.6 million for research services last year, mainly the sale of 2 million mice.

Charles River markets 165 different types of research models, including hamsters, guinea pigs, and immunodeficient, hairless "nude mice" useful for AIDS and cancer research.

It previously marketed other fat strains but this year came out with three new types predisposed to obesity. The JCR in particular was awaited by many because its arteries are prone to clog with plaque just like the arteries of people who eat a lot of french fries, but unlike most lab rats. The JCR was developed by James C. Russell, a surgical researcher at the University of Alberta, who selectively bred the rat strain in the 1980s to study its metabolism and failing arteries.

But it wasn't until several years ago that anyone expressed interested in licensing the rat, as research interest increased.

"Finally people have realized what a serious problem obesity is," Russell said in a telephone interview. "It's not just aesthetics, it's that people die early and miserably from advanced heart disease."

JCRs are born looking like other rats, and only a quarter of them grow to become obese. Typical lab rats consume 15 grams of food a day to feed their 150-gram bodies, but JCRs eat almost twice as much, and bulk up even though they're fed a typical health-food diet of grains and fish meal that's just 4 percent fat.

The husky critters look ragged by nine months of age and usually suffer serious cardiac problems by 13 months. Just startling them can bring on a heart attack. At the Charles River campus in Wilmington, technicians keep several hundred JCRs in large "isolator" cabinets sealed with plastic to protect them from germs.

Eventually, the animals will move to a facility in Michigan, but for now they live in plastic tubs slightly bigger than shoeboxes, two to five apiece, lined with wood shavings. Their docility gives them a pleasant personality, unlike Templeton, the pushy rat from "Charlotte's Web." At Nutrition 21, researcher Manley R. Finch said his 8-year-old daughter asked for a JCR as a pet after seeing a picture of one.

"She thought it was a teddy bear," Finch said. He nixed the idea because of the rat's short lifespan and the three cats already at home.

Ross Kerber can be reached at kerber@globe.com.

Heavy rats
Known as the JCR, after the initials of its Canadian developer, the rat is an all-American breed for scientists. Public health officials report epidemic rates of heart disease, diabetes, and other health problems across the United States stemming from a population bulking up on a fast-food diet and a sedentary lifestyle. Known as the JCR, after the initials of its Canadian developer, the rat is an all-American breed for scientists. Public health officials report epidemic rates of heart disease, diabetes, and other health problems across the United States stemming from a population bulking up on a fast-food diet and a sedentary lifestyle. (Globe Staff Photo)
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